Association between activating KIR and Perianal Crohn’s Disease in Pediatric Patients: A Nested case–control study

Association between activating KIR and Perianal Crohn’s Disease in Pediatric Patients: A Nested case–control study | Research Square window.SnipcartSettings = { analytics: { enabled: false } }; (function() { var accessVector = localStorage.getItem('access_vector') || ''; window.dataLayer = window.dataLayer || []; if (accessVector) { window.dataLayer.push({ user: { profile: { profileInfo: { snid: accessVector } } } }); } })(); (function(w,d,s,l,i){w[l]=w[l]||[];w[l].push({'gtm.start':new Date().getTime(),event:'gtm.js'});var f=d.getElementsByTagName(s)[0],j=d.createElement(s),dl=l!='dataLayer'?'&l='+l:'';j.async=true;j.src='https://www.googletagmanager.com/gtm.js?id='+i+dl;f.parentNode.insertBefore(j,f);})(window,document,'script','dataLayer','GTM-K279D39R'); Browse Preprints In Review Journals COVID-19 Preprints AJE Video Bytes Research Tools Research Promotion AJE Professional Editing AJE Rubriq About Preprint Platform In Review Editorial Policies Our Team Advisory Board Help Center Sign In Submit a Preprint Cite Share Download PDF Article Association between activating KIR and Perianal Crohn’s Disease in Pediatric Patients: A Nested case–control study Zhongsu Yu, Huajian Hu, Liangping Cheng This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-7953845/v1 This work is licensed under a CC BY 4.0 License Status: Under Review Version 1 posted 12 You are reading this latest preprint version Abstract Objective : Perianal Crohn’s disease (PCD) is a severe complication of Crohn’s disease (CD) that significantly impacts the quality of life in pediatric patients. This study aims to investigate the clinical risk factors associated with PCD, particularly focusing on the role of Killer cell immunoglobulin-like receptor (KIR) gene present or not in a Canadian pediatric cohort. Methods : Data were collected from 1,021 individuals diagnosed with CD in Ottawa and Montreal, Canada. The study employed a cohort design to assess the association between KIR gene polymorphisms and the risk of developing PCD. Multivariable regression models were used to control for confounding variables such as age at diagnosis, gender, and disease location. The statistical analyses included descriptive statistics, propensity score matching, and inverse probability weighting to ensure robust results. Results : A total of 187 cases were analyzed, with 41 cases of PCD and 146 cases of non-perianal CD. The presence of KIR2DS5 was significantly associated with an increased risk of PCD (OR = 2.49, 95% CI: 1.09–5.69, P = 0.031) after adjusting for multiple covariates. Subgroup analyses revealed potential interaction effects based on ancestral origins, with French-ancestry children in Montreal showing a higher susceptibility to PCD when the activating KIR2DS5 present. Conclusion : The study demonstrates that KIR2DS5 is a significant genetic risk factor for PCD in pediatric patients. This finding highlights the importance of genetic factors in the pathogenesis of PD and suggests that KIR2DS5 genotyping could serve as a potential biomarker for identifying high-risk pediatric patients with CD. Future research should focus on validating these findings in larger and more diverse populations and exploring targeted therapies based on genetic profiles. Health sciences/Diseases Health sciences/Gastroenterology Biological sciences/Genetics Biological sciences/Immunology Health sciences/Medical research Health sciences/Risk factors KIR2DS5 Perianal Crohn’s Disease (PCD) Pediatric Crohn’s Disease Genetic Risk Factors Cohort Study Figures Figure 1 Figure 2 Introduction Perianal Crohn’s disease (PCD) [ 1 ] is a complex and debilitating condition associated with Crohn’s disease, characterized by various perianal manifestations including anal skin lesions, fissures, ulcers, strictures, fistulas, and abscesses. The impact of PCD on patients is profound [ 2 , 3 ] , as it causes significant pain, difficulty in defecation, and even fecal incontinence, leading to a considerable burden on healthcare resources. Despite advancements in clinical, radiological, endoscopic, and histopathological techniques for diagnosis and management, early detection and effective treatment options remain limited, particularly in pediatric populations. This highlights the urgent need for further research into the clinical factors influencing the risk and progression of PCD. Previous studies have established associations between genetic factors and various autoimmune diseases, with a particular focus on the role of killer cell immunoglobulin-like receptors (KIR) [ 4 ] genes. However, the specific contribution of KIR gene polymorphisms to the risk of developing Crohn’s disease and its perianal manifestations has yet to be fully elucidated. Notably, prior research has suggested that KIR gene variations may influence immune responses [ 5 , 6 ] , affecting the susceptibility and pathogenesis of autoimmune conditions, including inflammatory bowel diseases such as Crohn’s disease. This underscores the potential for a deeper understanding of KIR gene involvement in the etiology of PCD, which has not been thoroughly explored in existing literature. Convergent evidence from prior investigations [ 3 , 4 , 7 – 10 ] demonstrates that KIR polymorphisms calibrate the activation threshold and qualitative profile of immune responses in autoimmune disorders, including Crohn’s disease, by modulating the effector functions of NK and T lymphocytes. Synthesizing these findings implicates KIR variation as a pivotal determinant of disease phenotype, thereby furnishing a mechanistic framework for the present study on perianal Crohn’s disease and underscoring its translational relevance. The present study employs a cohort design to investigate the association between KIR gene polymorphisms and the risk of PCD among Crohn’s disease patients. Data were collected from 1,021 individuals diagnosed with Crohn’s disease in Ottawa and Montreal, with a focus on identifying those who developed perianal complications. This study design allows for the effective control of confounding variables and enhances the robustness of the findings through the inclusion of a well-defined control group. This study elucidates the genetic architecture and immunopathogenesis underlying perianal Crohn’s disease (PCD) by systematically interrogating KIR gene polymorphisms, thereby identifying novel biomarkers that enable early risk stratification and precision therapeutic targeting to substantially improve clinical outcomes. Materials and Methods Data Sources KIR genotype data Genotype data on KIR activating genes for subjects from two cities in Canada. Activating Killer-cell Immunoglobulin-like Receptor genes confer risk for Crohn’s disease in children of the Western European descent: Findings based on case-control studies [ 4 ] .Ethical approval and consent were not required as this study was based on publicly available de-identified data. This study complied with the Strengthening the Reporting of Observational Studies in Epidemiology (STROBE) reporting guideline. Study Design and Population Primary article data had carried out a case-control study based on cohorts acquired from three gastroenterology clinics at Ottawa, Montreal, and Winnipeg, in Canada [ 4 ] . The Ottawa cohort comprised unrelated cases and controls of white (Western European) origin (cases = 93, controls = 120) and the Montreal cohort comprised of Caucasian unrelated cases and controls that were exclusively of French ancestry (cases = 193, controls = 245). The diagnosis of the CD cases was based on standard criteria that included clinical, radiological, endoscopic and histopathological findings [ 11 ] . As KIR genes frequencies may vary between apparently ethnically homogeneous populations, we selected controls from different sources to enhance population representation. These included children visiting the orthopaedic department of the study hospital for minor fractures (Ottawa and Montreal), their siblings (Montreal), a random sample of population-based children (Montreal) and a birth cohort (Montreal). Only healthy controls without any cancer or autoimmune disorders were included. A subset of the control subjects from Ottawa and Montreal have been previously utilized for replicating or confirming associations between reported susceptibility genes (viz. NOD2, ATG16L1, IL23R, IL10, STAT3, ZNF365, PTPN2, locus 20q13 etc.) and CD in Canadian children [ 4 , 12 – 16 ] . This study’s case selected from the Crohn's disease cohort in Ottawa and Montreal(Fig. 1 ). Initially, there were a total of 1021 cases, from which 565 control cases were excluded. Among the remaining 456 cases, an additional 170 were excluded due to missing information on age at diagnosis and gender, leaving 286 cases. From these 286 cases, 99 more were excluded due to missing information on disease location and behavior, resulting in a final count of 187 cases. These 187 cases were categorized into two groups: non-perianal Crohn's disease (n = 146) and perianal Crohn's disease (n = 41). Outcomes: Perianal Crohn’s Disease Perianal Crohn's disease (PCD) is defined as a severe and distinct clinical manifestation of Crohn's disease (CD), a chronic, relapsing, immune-mediated inflammatory bowel disease (IBD). PCD specifically involves inflammation and complications localized to the perianal region, which encompasses the skin and soft tissues surrounding the anus. It represents a major complication of CD, affecting a significant subset of patients, with reported prevalence ranging from 17% to 43% of all CD cases [ 17 ] . Diagnosis requires a high index of suspicion, especially in patients presenting with refractory perianal disease. It involves a combination of clinical assessment, detailed anorectal examination (often necessitating examination under anesthesia - EUA), and advanced imaging techniques such as pelvic Magnetic Resonance Imaging (MRI) or Endoanal Ultrasound to define the anatomy of fistulas and abscesses and guide management [ 18 ] . Management is inherently challenging and necessitates a multidisciplinary approach involving gastroenterologists, colorectal surgeons, radiologists, and specialized nurses. Treatment goals focus on controlling active inflammation, managing sepsis (primarily through drainage of abscesses and placement of non-cutting setons), promoting fistula healing, preventing recurrence, preserving sphincter function, and improving quality of life. Therapeutic strategies include antibiotics, immunosuppressants (e.g., thiopurines), biologic agents (particularly anti-TNF-α agents like infliximab which have shown efficacy in modulating the local immune imbalance and promoting healing), and surgical interventions ranging from simple drainage and seton placement to more complex procedures like fistulotomy (for select simple fistulas), advancement flaps, ligation of intersphincteric fistula tract (LIFT), and potentially fecal diversion or proctectomy in severe, refractory cases. Despite advances, PCD remains a significant cause of long-term disability in CD patients, associated with a higher risk of perianal cancer due to chronic inflammation [ 18 – 20 ] .Outcomes classification based on the WGO’s Montreal Classification. Activating KIR2DS5 gene status and Prognostic Implications in PCD The activating receptor KIR2DS5, expressed on natural killer (NK) cells, regulates immune responses through its short cytoplasmic domain binding TYRO proteins. This gene exhibits high polymorphism, with allele frequencies varying ethnically predominates in European populations, where mutations in critical extracellular residues (e.g., S111, F164) disrupt glycosylation, causing functional instability. Conversely, KIR2DS5 other mutation is frequent in African populations and confers protective effects via HLA-C2-specific binding. In CD, KIR2DS5 is a significant risk factor, with large-scale case-control studies confirming robust associations between its presence and increased CD susceptibility (OR = 3.06, 95% CI: 2.36–3.97; P = 1.35 × 10 − 17 ) [ 4 ] . This risk persists across pediatric and adult Western European cohorts, suggesting a pathogenic role in disease progression. Mechanistically, KIR2DS5 enhances NK cell-mediated cytotoxicity and pro-inflammatory cytokine release (e.g., IFN-γ), exacerbating intestinal mucosal inflammation. Consequently, KIR2DS5 allelic genotyping may serve as a biomarker for risk stratification and prognostic assessment in high-susceptibility CD populations.The detection of a DNA band of the expected molecular weight was considered as the presence of the gene in the genomic DNA sample.The presence or absence of each activating KIR in all cases and controls was determined by using PCR and sequence-specific primers on their genomic DNA samples as described [ 4 ] . Covariate The covariates in this study are: Gender (dichotomous), Age at diagnosis (continuous). Due to skewness, Age at diagnose is grouped into 15 years. Center/race represents ancestry: Montreal (French) and Ottawa (Caucasian). Disease location is classified as L1 ± L4, L2 ± L4, or L3 ± L4. Activating KIR gene status is categorized based on literature [ 4 ] . For the outcome variable, the study focuses on perianal disease. The original 3 - category variable (B1 ± p, B2 ± p, B3 ± p) is converted to a binary variable: non - perianal Crohn's disease vs Perianal Crohn’s disease. Statistical Analyses Descriptive analysis was performed on all participants, patient characteristics were described overall and stratified by group (outcome groups: isolated non-perianal Crohn's disease versus perianal Crohn's disease). Continuous data were expressed as median (interquartile range) based on normality distribution. Categorical variables were presented as percentages and analyzed using the Chi-square test. Based on the adjustment models detailed in the study design, three hierarchical multivariable regression models were implemented to evaluate the association between KIR2DS5 and Crohn's disease (CD) risk while controlling for key covariates: Model 1 adjusted for core demographic variables including gender, age at diagnosis, and combined recruitment center/ancestral background (Montreal cohort: French ancestry; Ottawa cohort: Caucasian ancestry) to account for population stratification. Model 2 further adjusted for the covariates in Model 1 plus disease location (e.g., ileal, colonic, or ileocolonic involvement) to address potential confounding by CD phenotypic heterogeneity. Model 3 expanded adjustment to include covariates from Model 2 and the presence/absence of other functionally relevant KIR genes (KIR2DS1, KIR2DS2, KIR2DS3, KIR2DS4a, KIR2DS4b, and KIR3DS1), thereby isolating the independent effect of KIR2DS5 beyond linkage disequilibrium or epistatic interactions within the KIR gene cluster . Propensity score matching (PSM) was used to adjust for confounders between the different groups. Using the estimated propensity scores as weights, an inverse probability weighting (IPW) model was used to generate a weighted cohort [ 21 ] .The probability of diagnosed with PCD was estimated using a logistic regression for each patient. We matched the two groups in a 1:1 ratio with a caliper width of 0.2. The standardized mean difference (SMD) was used to examine the degree of PSM. This tiered approach rigorously controlled for: Population-specific genetic background: Ancestry groups were stratified by recruitment center (Montreal/Ottawa) to mitigate population structure bias, consistent with established protocols for genetic association studies in admixed cohorts .Clinical heterogeneity: Inclusion of disease location (Montreal Classification) accounted for documented variations in disease behavior and severity .KIR-specific confounding: Adjustment for co-inherited activating KIR genes (KIR2DS1-3, KIR2DS4a/b, KIR3DS1) addressed haplotype-driven effects, as KIR genes exhibit strong linkage disequilibrium on chromosome 19q13.4 .The models employed multivariable logistic regression with statistical significance defined as P < 0.05 (two-tailed), aligning with methodologies in prior KIR-CD association studies . The statistical analyses were performed using FreeStatistics (version 2.1.1), a software package designed with user-friendly interfaces that facilitate common analyses and data visualization. This software relies on R as its core statistical engine, while its graphical user interface (GUI) is built using Python. Most analyses can be completed with just a few clicks, enhancing efficiency for reproducible analysis and interactive computing. FreeStatistics is developed by FreeClinical Medical Technology Co., Ltd, based in Beijing, China, and can be accessed at http://www.clinicalscientists.cn/freestatistics/ . Results Participants and Demographic Characteristics In the study of Crohn's disease (CD) cohorts from Ottawa and Montreal, a total of 1021 cases were initially identified. After excluding 565 control cases, 456 cases remained. Further exclusions were made due to missing data of age at diagnosis and gender (170 cases), disease location and behavior (99 cases), resulting in a final cohort of 187 cases (Fig. 1 ). These cases were categorized into non-perianal CD (n = 146) and perianal CD (n = 41) groups. The demographic and clinical characteristics of these groups are summarized in Table 1 . To investigate the distribution of present of activating KIR2DS5 gene in patients with Crohn's disease (CD) and its correlation with clinical characteristics.A total of 187 CD patients were included, among whom 76 did not carry the activating KIR2DS5 gene and 111 did. The results showed that the median age at diagnosis was 12.8 years, with no significant difference in the age at diagnosis between patients with and without the activating KIR2DS5 gene present (P = 0.597). In terms of age stratification, there was no significant difference in the proportion of patients with and without the activating KIR2DS5 gene in the 2.5–11 years, 12–15 years, and > 15 years age groups (P = 0.417). Regarding the distribution of centers and races, there was a significant difference in the proportion of patients with the activating KIR2DS5 gene between Montreal (French ancestry) and Ottawa (Caucasian ancestry) (P < 0.001), with a higher proportion of activating KIR2DS5 status carriers in Montreal. The proportion of male and female patients with and without the activating KIR2DS5 status showed no significant difference (P = 0.235). For other KIR genes, such as KIR2DS1, KIR2DS2, KIR3DS3, KIR2DS4a, KIR2DS4b, and KIR3DS1, there was no significant difference in their distribution between the two groups (P > 0.05), except for KIR2DS5, which was significantly different (P < 0.001), in patients without the activating KIR2DS5 gene. In terms of disease behavior and location, there was no significant difference in the proportion of patients with and without the activating KIR2DS5 gene status among those with non-perianal and perianal Crohn's disease (P = 0.187), as well as among those with different disease locations (L1 ± L4, L2 ± L4, L3 ± L4) (P = 0.327). Table 1 , Association Analysis of whether activating KIR2DS5 Gene present or not and Clinical Features in Patients with Crohn's Disease. Variables Total (n = 187) Activating KIR2DS5 absent (n = 76) Activating KIR2DS5 present (n = 111) P value Age at diagnose, Median (IQR) 12.8 (10.6, 14.6) 12.8 (10.9, 14.0) 12.8 (10.5, 14.7) 0.597 Age, n (%) 0.417 2.5 ~ 11y 73 (39.0) 34 (44.7) 39 (35.1) 12 ~ 15y 73 (39.0) 27 (35.5) 46 (41.4) > 15y 41 (21.9) 15 (19.7) 26 (23.4) Center/race, n (%) < 0.001 Montreal(French ancestry) 95 (50.8) 26 (34.2) 69 (62.2) Ottawa(Caucasian ancestry) 92 (49.2) 50 (65.8) 42 (37.8) Gender, n (%) 0.235 Female 91 (48.7) 33 (43.4) 58 (52.3) Male 96 (51.3) 43 (56.6) 53 (47.7) KIR2DS1, n (%) 0.81 Absent 46 (24.6) 18 (23.7) 28 (25.2) Present 141 (75.4) 58 (76.3) 83 (74.8) KIR2DS2, n (%) 0.517 Absent 49 (26.2) 18 (23.7) 31 (27.9) Present 138 (73.8) 58 (76.3) 80 (72.1) KIR3DS3, n (%) 0.944 Absent 88 (47.1) 36 (47.4) 52 (46.8) Present 99 (52.9) 40 (52.6) 59 (53.2) KIR2DS4a, n (%) 0.713 Absent 49 (26.2) 21 (27.6) 28 (25.2) Present 138 (73.8) 55 (72.4) 83 (74.8) KIR2DS4b, n (%) 0.713 Absent 49 (26.2) 21 (27.6) 28 (25.2) Present 138 (73.8) 55 (72.4) 83 (74.8) KIR2DS5, n (%) < 0.001 Absent 76 (40.6) 76 (100) 0 (0) Present 111 (59.4) 0 (0) 111 (100) KIR3DS1, n (%) 0.053 Absent 73 (39.0) 36 (47.4) 37 (33.3) Present 114 (61.0) 40 (52.6) 74 (66.7) Disease behavior, n (%)† 0.187 non-perianal Crohn's disease 146 (78.1) 63 (82.9) 83 (74.8) Perianal Crohn’s disease 41 (21.9) 13 (17.1) 28 (25.2) Disease location, n (%)† 0.327 L1 ± L4 38 (20.3) 19 (25) 19 (17.1) L2 ± L4 47 (25.1) 16 (21.1) 31 (27.9) L3 ± L4 102 (54.5) 41 (53.9) 61 (55) †Classification based on the WGO’s Montreal Classification. The age at diagnosis cut-off for study inclusion was 16 years in Ottawa and 20 years in Montreal. Four patients had disease restricted to either only the upper tract or anal region and for three patients the location could not be adequately classified. For two patients, the disease behaviour at diagnosis was not clear. The percentages may not add up due to rounding. Associations between present of activating KIR2DS5 and Perianal Crohn's disease (PCD) In the association analysis, various statistical models were employed to assess the association between the activating KIR2DS5 status and the risk of Perianal Crohn's disease (PCD), adjusting for potential confounding factors. The unmatched crude model indicated a potential association with an odds ratio (OR) of 1.63 (95% CI: 0.78–3.41, P = 0.19), which was not statistically significant(Table 2 ). However, after adjusting for multiple variables in the multivariable model, refer to activating KIR2DS5 absent groups, the odds ratio in activating KIR2DS5 present groups increased to 2.52 (95% CI: 1.1–5.76, P = 0.029), suggesting a statistically significant association(Table 2 ). Propensity score adjustment, which balances known confounding factors, yielded an OR of 2.44 (95% CI: 1.08–5.52, P = 0.032), similar to the multivariable adjusted model(Table 2 ). The inverse probability of treatment weighting (IPTW) model, which assigns weights to balance differences between groups, also showed a significant association with an OR of 2.53 (95% CI: 1.16–5.54, P = 0.02)(Table 3 ). Table 2 Association between the risk of Perianal Crohn’s disease and activating KIR2DS5 present or not. Model1 Model2 Model3 KIR2DS5 n Event(%) OR (95%CI) P value OR (95%CI) P value OR (95%CI) P value Absent 76 13 (17.1) 1(Ref) 1(Ref) 1(Ref) Present 111 28 (25.2) 2.44 (1.08 ~ 5.49) 0.032 2.4 (1.06 ~ 5.41) 0.035 2.49 (1.09 ~ 5.69) 0.031 •Model 1: Adjusts for gender, age at diagnosis and center/race. •Model 2: Adjusts for the covariates in Model 1 plus disease location. •Model 3: Adjusts for the covariates in Model 2 plus the presence of other KIR genes (KIR2DS1, KIR2DS2, KIR2DS3, KIR2DS4a, KIR2DS4b, KIR3DS1). Table 3 Sensitivity validation of the association between activated KIR2DS5 and perianal Crohn’s disease lesions using propensity-score-matched analysis Models Item1 OR (95%CI) P value Unmatched.crude Activating KIR2DS5: Present vs Absent 1.63 (0.78 ~ 3.41) 0.19 Multivariable.adjusted Activating KIR2DS5: Present vs Absent 2.52 (1.1 ~ 5.76) 0.029 PropensityScore.adjusted Activating KIR2DS5: Present vs Absent 2.44 (1.08 ~ 5.52) 0.032 Weighted.IPTW Activating KIR2DS5: Present vs Absent 2.53 (1.16 ~ 5.54) 0.02 The analysis results of the variable KIR2DS5 (Present vs Absent) under different statistical models, including the odds ratio (OR), 95% confidence interval (95% CI), and P-value. These models range from the unmatched crude model to those adjusted by various propensity score matching and weighting methods. Subgroup Analyses In the sensitivity subgroup analysis, the impact of the activating KIR2DS5 gene status on the risk of Perianal Crohn's disease (PCD) was assessed across various subgroups after adjusting for confounding factors. The results, as presented in Supp.Table 1 and the corresponding forest plot(Fig. 2 ), indicate stability across all subgroups(Supp.Table 1 ). Notably, the subgroup of different ancestral origins showed a P.for.interaction of 0.07, suggesting a potential interaction effect(Supp.Table 1 ,Fig. 2 ), but the P.value was not significant, maybe due to not so much cases, we need to colected more case in the future. Specifically, within the Montreal cohort, children of French ancestry with the SNP were found to be more susceptible to PCD, highlighting the presence of an interaction(Fig. 2 ). This finding underscores the importance of considering genetic ancestry in the context of present of activating KIR2DS5 and PCD risk(Fig. 2 ). Discussion Perianal Crohn’s disease (PCD) represents a significant complication of Crohn’s disease, characterized by various perianal manifestations, including perianal fistulas, abscesses, and skin tags. The multifaceted nature of PCD, coupled with its association with serious outcomes like anal cancer, underscores the urgent need for comprehensive research to enhance early diagnosis and effective management strategies for affected individuals [ 7 , 8 ] . In this study, we aimed to elucidate the relationship between killer cell immunoglobulin-like receptor (KIR) gene activating status and the risk of developing PCD. By analyzing clinical data from a cohort of 1,021 Crohn’s disease patients, ultimately narrowing our focus to 187 subjects, we sought to identify significant associations that may inform clinical practice. From a rigorously phenotyped paediatric Crohn’s disease (CD) cohort (n = 187, median age at diagnosis 12.8 years) derived from Ottawa (Caucasian) and Montréal (French-Canadian) centres, carriage of the activating KIR2DS5 status was markedly enriched in the Montréal population (P < 0.001). Multivariable logistic regression, propensity-score adjustment and inverse-probability-of-treatment weighting converged on a consistent and independent association between KIR2DS5 presence and perianal CD (adjusted OR 2.52, 95% CI 1.10–5.76, P = 0.029; OR 2.44, 1.08–5.52, P = 0.032; and OR 2.53, 1.16–5.54, P = 0.020, respectively), whereas no heterogeneity was observed across age strata, sex, or conventional Montreal classifications. Exploratory ancestry-stratified analyses revealed a trend toward stronger effect modification in children of French ancestry (Pinteraction = 0.07), underscoring the potential contribution of population-specific genetic background to KIR2DS5-mediated susceptibility to perianal CD.The findings indicate a notable divergence in KIR gene expression among patients with PCD, suggesting a potential role of these genes in modulating the disease’s pathogenesis. This discussion will delve into the implications of our findings, underscoring the importance of understanding the genetic predispositions that contribute to the clinical manifestations of PCD [ 6 , 22 ] . The association of activating KIR genes with the risk of perianal Crohn’s disease (PCD) presents promising implications for understanding the pathogenesis of this debilitating condition. Our findings indicate significant differences in KIR gene phenotypes among patients with PCD, particularly in the frequency of specific KIR genotypes. This suggests that KIR genes may play a pivotal role in modulating immune responses, potentially influencing the development and severity of Crohn’s disease manifestations. Previous studies have highlighted the importance of KIR and HLA interactions in various autoimmune diseases, suggesting a similar mechanism may underpin PCD. Notably, the presence of certain KIR genotypes has been correlated with autoimmune conditions, emphasizing their potential as biomarkers for assessing PCD risk[8]. Further investigation into the mechanisms through which KIR genes affect immune responses could pave the way for targeted therapeutic strategies aimed at mitigating the impact of PCD. The diverse clinical manifestations of PCD, including anal fissures and perianal abscesses, complicate its early diagnosis and management. Our analysis revealed that patients with PCD frequently present with a spectrum of symptoms, which may contribute to diagnostic delays. The variability in clinical presentation underlines the necessity for clinicians to maintain a high index of suspicion, particularly in pediatric populations where symptoms may be misattributed to less severe conditions. Early intervention has been shown to significantly influence disease progression and improve patient outcomes, highlighting the critical importance of recognizing and addressing these symptoms promptly [ 3 ] . The robust epidemiologic association between activating KIR2DS5 and paediatric perianal Crohn’s disease (PCD) suggests a mechanistic axis in which ligand–receptor engagement on mucosal natural killer (NK) and cytotoxic T cells lowers the activation threshold for type-1 cytokine release, thereby amplifying a TH1/TH17-biased inflammatory loop within the densely innervated anoderm. KIR2DS5 recognises HLA-C2 [ 4 , 5 , 23 – 25 ] and possibly non-classical MHC-I molecules that are up-regulated on stressed colonic epithelium; its activating ITAM-bearing tail recruits ZAP70/SYK kinases to trigger perforin/granzyme secretion and IFN-γ production [ 26 ] . In tissue niches already compromised by epithelial breach, this exaggerated effector response may accelerate fistulising cascades driven by IL-23–responsive γδ T cells and neutrophil extracellular traps. Importantly, the absence of association between PCD and other activating KIRs (KIR2DS1, 2DS2, 2DS4a/b, 3DS1) implies that these paralogues either engage low-affinity ligands under inflammatory conditions or are epigenetically silenced in the rectal mucosa. Furthermore, compensatory inhibitory KIR-KIR ligand interactions (e.g., KIR2DL3–HLA-C1) may counterbalance activating signals, explaining the neutral effect of KIR2DS4 deletions or KIR3DS1 polymorphisms on PCD penetrance. Collectively, the data delineate a gene-dosage model in which KIR2DS5 [ 27 ] emerges as the principal activating KIR that licences NK-mediated immunopathology in perianal Crohn’s disease, while other activating KIR variants remain mechanistically silent or are physiologically restrained by inhibitory checkpoints. The design of our cohort study effectively elucidates the relationship between KIR gene variation and PCD risk. By ensuring a representative sample and controlling for confounding variables, we bolster the reliability of our findings. This methodology allows for a clearer interpretation of how specific genetic markers may predispose individuals to PCD, potentially guiding future research and clinical practice. The robustness of the case-control design enhances its applicability in identifying high-risk populations, which is crucial for early diagnosis and intervention strategies [ 9 ] . Future studies could further refine these methodologies to explore additional genetic and environmental factors influencing PCD risk. The demographic diversity of our study population strengthens the generalizability of our results. By including individuals from varied ethnic backgrounds, we can better understand how genetic factors may differ across populations and contribute to PCD prevalence. This diversity highlights the need for further research into the genetic epidemiology of PCD, particularly in underrepresented groups. Understanding ethnic variations in KIR gene distribution could illuminate differences in disease susceptibility and inform culturally competent clinical practices. Comparative studies across diverse populations will be essential to delineate the role of genetic factors in the pathogenesis of PCD and other related autoimmune diseases [ 28 ] . In summary, our research underscores the potential of KIR genes as critical players in the etiology of PCD. The findings not only enhance our understanding of the disease but also open new avenues for targeted interventions and personalized treatment strategies. Continued exploration of KIR gene interactions and their implications for immune regulation will be crucial for developing effective therapeutic approaches for PCD and similar autoimmune conditions. Future studies should focus on the translational potential of these findings, aiming to integrate genetic insights into clinical practice and improve patient outcomes [ 6 ] . The limitations of this study include a sample size only 187 cases were categorized into two groups: non-perianal Crohn's disease (n = 146) and perianal Crohn's disease (n = 41), which may affect the generalizability of the findings. Although the cohort was derived from diverse ethnic backgrounds, the limited number of cases may restrict the robustness of the conclusions drawn regarding the association between KIR genes and perianal Crohn’s disease. Additionally, the lack of clinical validation analysis may hinder the ability to translate these findings into practical applications. Variability in the data collection process and potential inter-study differences could also introduce biases that influence the results. Therefore, further research with larger cohorts and stringent validation methodologies is critical to substantiate the observed associations. Conclusion In conclusion, this study highlights the significant association between KIR genes and perianal Crohn’s disease, underscoring the importance of diverse participant samples in identifying risk factors. The findings pave the way for future investigations aimed at elucidating the roles of KIR genes and their interactions with other immune-related genes. Such research is essential for the development of personalized treatment strategies and innovative interventions for perianal Crohn’s disease, ultimately improving patient outcomes. Declarations Acknowledgments We appreciate Dr. Jie Liu of the Department of Vascular and Endovascular Surgery, Chinese PLA General Hospital & Physician-Scientist Center of China for statistics, study deign consultations and editing the manuscript. Statement of Ethics Ethical approval and consent were not required as this study was based on publicly available de-identified data. Conflict of Interest Statement The remaining authors declare that they have no conflict of interest. Funding Sources Liangping Cheng, Talent Introduction Startup Fund, Grant ID:4000036 Author Contributions Zhongsu Yu: conceptualization, formal analysis, and writing-original draft.Huajian Hu: formal analysis and writing-original draft. Liangping Cheng: writing-review and editing-and project administration. All authors contributed to and approved the final manuscript. Data Availability Statement Raw relevant data are deposited on Dryad. (https://datadryad.org/dataset/doi:10.5061/dryad.1q5q65g). Further inquiries can be directed to the corresponding author. References Parian, A. M. et al. Management of perianal crohn’s disease[J]. Am. J. Gastroenterol. 118 (8), 1323–1331 (2023). Ohad Atia, N. et al. Perianal crohn’s disease is associated with poor disease outcome: a nationwide study from the epiIIRN cohort[J] Vol. 20, e484–e495 (Clinical Gastroenterology and Hepatology, W.B. Saunders, 2022). 3. Johansen, M. P. et al. Perianal crohn’s disease and the development of colorectal and anal cancer: a systematic review and meta-analysis[J] Vol. 17, 361–368 (Journal of Crohn’s & Colitis, 2023). 3. Samarani, S. et al. Activating Killer-cell Immunoglobulin-like Receptor genes confer risk for Crohn’s disease in children and adults of the Western European descent: Findings based on case-control studies[J]. PLOS One, Public Library of Science, 14(6): e0217767. (2019). Della Chiesa, M. et al. Evidence that the KIR2DS5 gene codes for a surface receptor triggering natural killer cell function[J]. Eur. J. Immunol. 38 (8), 2284–2289 (2008). Elagab, E. A. et al. Role of centromeric and telomeric haplotypes of killer-cell immunoglobulin-like receptors (KIRs) in disease susceptibility: a research review[J]. Cureus 17 (5), e83728 (2025). Kotsafti, A. et al. Fistula-related cancer in crohn’s disease: a systematic review[J]. Cancers 13 (6), 1445 (2021). Boarini, L. R. et al. Perianal fistulizing crohn’s disease is associated with a higher prevalence of HPV in the anorectal fistula tract. A comparative study[J]. Clinics (sao Paulo, Brazil), 78: 100219. (2023). Jin, S. et al. Prediction of postoperative recurrence of perianal fistulizing crohn’s disease by fecal calprotectin combined with serum miRNA6086[J]. J. Int. Med. Res. 53 (4), 3000605251328245 (2025). Chen, Z-X. et al. Risk factors for recurrence after bowel resection for crohn’s disease[J]. World J. Gastrointest. Pharmacol. 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Susceptibility loci reported in genome-wide association studies are associated with crohn’s disease in canadian children[J] Vol. 31, 1186–1191 (Alimentary Pharmacology & Therapeutics, 2010). 11. Zhiwei, L., Feihu, Y. & Chunfang, G. Advances in surgical diagnosis and treatment of perianal fistulizing Crohn’s disease[J]. J. Colorectal Anal. Surg. 31 (1), 82–88 (2025). Sordo-Mejia, R. & Gaertner, W. B. Multidisciplinary and evidence-based management of fistulizing perianal crohn’s disease[J]. World J. Gastrointest. Pathophysiology . 5 (3), 239–251 (2014). Guzela, V. R. Há maior frequência de displasia e infecção anal pelo papilomavírus humano na doença de crohn?[D] (Universidade de São Paulo, 2022). McLellan, P. & Kirchgesner, J. Perianal fistulizing Crohn’s disease and overall risk of cancer: No red flag[J]. United Eur. Gastroenterol. J. 11 (5), 401–402 (2023). Xia, J. et al. Association between statin use on delirium and 30-day mortality in patients with chronic obstructive pulmonary disease in the intensive care unit[J]. Eur. J. Med. Res. 28 (1), 572 (2023). Ramírez, S. et al. Association of KIR2DL2 gene with anti-cyclic citrullinated protein antibodies for serodiagnosis in rheumatoid arthritis[J]. Medicina 79 (3), 161–166 (2019). Stewart, C. A., Laugier-Anfossi, F., Vély, F. & 等 Recognition of peptide-MHC class I complexes by activating killer immunoglobulin-like receptors[J]. Proc. Natl. Acad. Sci. U.S.A. 102 (37), 13224–13229 (2005). Hollenbach, J. A. et al. Susceptibility to crohn’s disease is mediated by KIR2DL2/KIR2DL3 heterozygosity and the HLA-C ligand[J]. Immunogenetics 61 (10), 663–671 (2009). Steiner, N. K. et al. Extracellular domain alterations impact surface expression of stimulatory natural killer cell receptor KIR2DS5[J]. Immunogenetics 60 (11), 655–667 (2008). Association between KIR-HLA combination. and ulcerative colitis and crohn’s disease in a japanese population | PLOS one[EB/OL]. [2025-08- 30].https://journals.plos.org/plosone/article?id=10.1371/journal.pone.0195778 Fathollahi, A. et al. The role of killer-cell immunoglobulin-like receptor (KIR) genes in susceptibility to inflammatory bowel disease: systematic review and meta-analysis[J]. Inflamm. Research: Official J. Eur. Histamine Res. Soc. … et Al] . 67 (9), 727–736 (2018). Ritari, J. et al. Disease associations of natural killer (NK) cell KIR gene content variation in 352,783 finns[J]. Hum. Immunol. 85 (6), 111177 (2024). Additional Declarations No competing interests reported. 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1","display":"","copyAsset":false,"role":"figure","size":90212,"visible":true,"origin":"","legend":"\u003cp\u003eFlowchart of the Crohn's disease cohort selection process. This figure illustrates the process of case selection from the Crohn's disease cohort in Ottawa and Montreal. Initially, there were a total of 1021 cases, from which 565 control cases were excluded. Among the remaining 456 cases, an additional 170 were excluded missing age/gender at diagnosis, leaving 286 cases. From these 286 cases, 99 more were excluded due to missing information on disease location and behavior, resulting in a final count of 187 cases. These 187 cases were categorized into two groups: non-perianal Crohn's disease (n=146) and perianal Crohn's disease (n=41).\u003c/p\u003e","description":"","filename":"1.png","url":"https://assets-eu.researchsquare.com/files/rs-7953845/v1/f73c2edaa7903da3bb199e00.png"},{"id":96708112,"identity":"f39cb320-054d-4128-81dd-6ca7e7275f2e","added_by":"auto","created_at":"2025-11-25 09:57:00","extension":"png","order_by":2,"title":"Figure 2","display":"","copyAsset":false,"role":"figure","size":127047,"visible":true,"origin":"","legend":"\u003cp\u003eThe figure illustrates the association between the presence or absence of activating KIR2DS5 and various subgroups, including age at diagnosis, gender, center/race, and specific KIR genes. The odds ratios (OR) and their 95% confidence intervals (CI) are presented for each subgroup, along with a P-value for interaction to assess the significance of the differences observed across subgroups.\u003c/p\u003e","description":"","filename":"2.png","url":"https://assets-eu.researchsquare.com/files/rs-7953845/v1/e8e28b247b93f2c71810e372.png"},{"id":96913343,"identity":"99425f2d-0aa4-4f19-a5ce-1f67f1413ddd","added_by":"auto","created_at":"2025-11-27 13:58:58","extension":"pdf","order_by":0,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":1062501,"visible":true,"origin":"","legend":"","description":"","filename":"manuscript.pdf","url":"https://assets-eu.researchsquare.com/files/rs-7953845/v1/45403efc-84bc-4249-b37b-1203cfccf62e.pdf"},{"id":96708314,"identity":"4f69eb7e-c301-4e0a-b386-60108c759662","added_by":"auto","created_at":"2025-11-25 10:00:59","extension":"docx","order_by":1,"title":"","display":"","copyAsset":false,"role":"supplement","size":23332,"visible":true,"origin":"","legend":"","description":"","filename":"Supp.docx","url":"https://assets-eu.researchsquare.com/files/rs-7953845/v1/a8854ac3cdb205604c4a561c.docx"}],"financialInterests":"No competing interests reported.","formattedTitle":"Association between activating KIR and Perianal Crohn’s Disease in Pediatric Patients: A Nested case–control study","fulltext":[{"header":"Introduction","content":"\u003cp\u003ePerianal Crohn\u0026rsquo;s disease (PCD)\u003csup\u003e[\u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e1\u003c/span\u003e]\u003c/sup\u003e is a complex and debilitating condition associated with Crohn\u0026rsquo;s disease, characterized by various perianal manifestations including anal skin lesions, fissures, ulcers, strictures, fistulas, and abscesses. The impact of PCD on patients is profound\u003csup\u003e[\u003cspan citationid=\"CR2\" class=\"CitationRef\"\u003e2\u003c/span\u003e, \u003cspan citationid=\"CR3\" class=\"CitationRef\"\u003e3\u003c/span\u003e]\u003c/sup\u003e, as it causes significant pain, difficulty in defecation, and even fecal incontinence, leading to a considerable burden on healthcare resources. Despite advancements in clinical, radiological, endoscopic, and histopathological techniques for diagnosis and management, early detection and effective treatment options remain limited, particularly in pediatric populations. This highlights the urgent need for further research into the clinical factors influencing the risk and progression of PCD.\u003c/p\u003e\u003cp\u003ePrevious studies have established associations between genetic factors and various autoimmune diseases, with a particular focus on the role of killer cell immunoglobulin-like receptors (KIR)\u003csup\u003e[\u003cspan citationid=\"CR4\" class=\"CitationRef\"\u003e4\u003c/span\u003e]\u003c/sup\u003e genes. However, the specific contribution of KIR gene polymorphisms to the risk of developing Crohn\u0026rsquo;s disease and its perianal manifestations has yet to be fully elucidated. Notably, prior research has suggested that KIR gene variations may influence immune responses\u003csup\u003e[\u003cspan citationid=\"CR5\" class=\"CitationRef\"\u003e5\u003c/span\u003e, \u003cspan citationid=\"CR6\" class=\"CitationRef\"\u003e6\u003c/span\u003e]\u003c/sup\u003e, affecting the susceptibility and pathogenesis of autoimmune conditions, including inflammatory bowel diseases such as Crohn\u0026rsquo;s disease. This underscores the potential for a deeper understanding of KIR gene involvement in the etiology of PCD, which has not been thoroughly explored in existing literature.\u003c/p\u003e\u003cp\u003eConvergent evidence from prior investigations\u003csup\u003e[\u003cspan citationid=\"CR3\" class=\"CitationRef\"\u003e3\u003c/span\u003e, \u003cspan citationid=\"CR4\" class=\"CitationRef\"\u003e4\u003c/span\u003e, \u003cspan additionalcitationids=\"CR8 CR9\" citationid=\"CR7\" class=\"CitationRef\"\u003e7\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR10\" class=\"CitationRef\"\u003e10\u003c/span\u003e]\u003c/sup\u003edemonstrates that KIR polymorphisms calibrate the activation threshold and qualitative profile of immune responses in autoimmune disorders, including Crohn\u0026rsquo;s disease, by modulating the effector functions of NK and T lymphocytes. Synthesizing these findings implicates KIR variation as a pivotal determinant of disease phenotype, thereby furnishing a mechanistic framework for the present study on perianal Crohn\u0026rsquo;s disease and underscoring its translational relevance.\u003c/p\u003e\u003cp\u003eThe present study employs a cohort design to investigate the association between KIR gene polymorphisms and the risk of PCD among Crohn\u0026rsquo;s disease patients. Data were collected from 1,021 individuals diagnosed with Crohn\u0026rsquo;s disease in Ottawa and Montreal, with a focus on identifying those who developed perianal complications. This study design allows for the effective control of confounding variables and enhances the robustness of the findings through the inclusion of a well-defined control group. This study elucidates the genetic architecture and immunopathogenesis underlying perianal Crohn\u0026rsquo;s disease (PCD) by systematically interrogating KIR gene polymorphisms, thereby identifying novel biomarkers that enable early risk stratification and precision therapeutic targeting to substantially improve clinical outcomes.\u003c/p\u003e"},{"header":"Materials and Methods","content":"\u003cdiv id=\"Sec3\" class=\"Section2\"\u003e\u003ch2\u003eData Sources\u003c/h2\u003e\u003cdiv id=\"Sec4\" class=\"Section3\"\u003e\u003ch2\u003eKIR genotype data\u003c/h2\u003e\u003cp\u003eGenotype data on KIR activating genes for subjects from two cities in Canada. Activating Killer-cell Immunoglobulin-like Receptor genes confer risk for Crohn\u0026rsquo;s disease in children of the Western European descent: Findings based on case-control studies\u003csup\u003e[\u003cspan citationid=\"CR4\" class=\"CitationRef\"\u003e4\u003c/span\u003e]\u003c/sup\u003e.Ethical approval and consent were not required as this study was based on publicly available de-identified data. This study complied with the Strengthening the Reporting of Observational Studies in Epidemiology (STROBE) reporting guideline.\u003c/p\u003e\u003c/div\u003e\u003c/div\u003e\n\u003ch3\u003eStudy Design and Population\u003c/h3\u003e\n\u003cp\u003ePrimary article data had carried out a case-control study based on cohorts acquired from three gastroenterology clinics at Ottawa, Montreal, and Winnipeg, in Canada\u003csup\u003e[\u003cspan citationid=\"CR4\" class=\"CitationRef\"\u003e4\u003c/span\u003e]\u003c/sup\u003e. The Ottawa cohort comprised unrelated cases and controls of white (Western European) origin (cases\u0026thinsp;=\u0026thinsp;93, controls\u0026thinsp;=\u0026thinsp;120) and the Montreal cohort comprised of Caucasian unrelated cases and controls that were exclusively of French ancestry (cases\u0026thinsp;=\u0026thinsp;193, controls\u0026thinsp;=\u0026thinsp;245). The diagnosis of the CD cases was based on standard criteria that included clinical, radiological, endoscopic and histopathological findings\u003csup\u003e[\u003cspan citationid=\"CR11\" class=\"CitationRef\"\u003e11\u003c/span\u003e]\u003c/sup\u003e. As KIR genes frequencies may vary between apparently ethnically homogeneous populations, we selected controls from different sources to enhance population representation. These included children visiting the orthopaedic department of the study hospital for minor fractures (Ottawa and Montreal), their siblings (Montreal), a random sample of population-based children (Montreal) and a birth cohort (Montreal). Only healthy controls without any cancer or autoimmune disorders were included. A subset of the control subjects from Ottawa and Montreal have been previously utilized for replicating or confirming associations between reported susceptibility genes (viz. NOD2, ATG16L1, IL23R, IL10, STAT3, ZNF365, PTPN2, locus 20q13 etc.) and CD in Canadian children \u003csup\u003e[\u003cspan citationid=\"CR4\" class=\"CitationRef\"\u003e4\u003c/span\u003e, \u003cspan additionalcitationids=\"CR13 CR14 CR15\" citationid=\"CR12\" class=\"CitationRef\"\u003e12\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR16\" class=\"CitationRef\"\u003e16\u003c/span\u003e]\u003c/sup\u003e.\u003c/p\u003e\u003cp\u003eThis study\u0026rsquo;s case selected from the Crohn's disease cohort in Ottawa and Montreal(Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003e). Initially, there were a total of 1021 cases, from which 565 control cases were excluded. Among the remaining 456 cases, an additional 170 were excluded due to missing information on age at diagnosis and gender, leaving 286 cases. From these 286 cases, 99 more were excluded due to missing information on disease location and behavior, resulting in a final count of 187 cases. These 187 cases were categorized into two groups: non-perianal Crohn's disease (n\u0026thinsp;=\u0026thinsp;146) and perianal Crohn's disease (n\u0026thinsp;=\u0026thinsp;41).\u003c/p\u003e\u003cp\u003e\u003c/p\u003e\n\u003ch3\u003eOutcomes: Perianal Crohn’s Disease\u003c/h3\u003e\n\u003cp\u003ePerianal Crohn's disease (PCD) is defined as a severe and distinct clinical manifestation of Crohn's disease (CD), a chronic, relapsing, immune-mediated inflammatory bowel disease (IBD). PCD specifically involves inflammation and complications localized to the perianal region, which encompasses the skin and soft tissues surrounding the anus. It represents a major complication of CD, affecting a significant subset of patients, with reported prevalence ranging from 17% to 43% of all CD cases\u003csup\u003e[\u003cspan citationid=\"CR17\" class=\"CitationRef\"\u003e17\u003c/span\u003e]\u003c/sup\u003e.\u003c/p\u003e\u003cp\u003eDiagnosis requires a high index of suspicion, especially in patients presenting with refractory perianal disease. It involves a combination of clinical assessment, detailed anorectal examination (often necessitating examination under anesthesia - EUA), and advanced imaging techniques such as pelvic Magnetic Resonance Imaging (MRI) or Endoanal Ultrasound to define the anatomy of fistulas and abscesses and guide management\u003csup\u003e[\u003cspan citationid=\"CR18\" class=\"CitationRef\"\u003e18\u003c/span\u003e]\u003c/sup\u003e. Management is inherently challenging and necessitates a multidisciplinary approach involving gastroenterologists, colorectal surgeons, radiologists, and specialized nurses. Treatment goals focus on controlling active inflammation, managing sepsis (primarily through drainage of abscesses and placement of non-cutting setons), promoting fistula healing, preventing recurrence, preserving sphincter function, and improving quality of life. Therapeutic strategies include antibiotics, immunosuppressants (e.g., thiopurines), biologic agents (particularly anti-TNF-α agents like infliximab which have shown efficacy in modulating the local immune imbalance and promoting healing), and surgical interventions ranging from simple drainage and seton placement to more complex procedures like fistulotomy (for select simple fistulas), advancement flaps, ligation of intersphincteric fistula tract (LIFT), and potentially fecal diversion or proctectomy in severe, refractory cases. Despite advances, PCD remains a significant cause of long-term disability in CD patients, associated with a higher risk of perianal cancer due to chronic inflammation\u003csup\u003e[\u003cspan additionalcitationids=\"CR19\" citationid=\"CR18\" class=\"CitationRef\"\u003e18\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR20\" class=\"CitationRef\"\u003e20\u003c/span\u003e]\u003c/sup\u003e.Outcomes classification based on the WGO\u0026rsquo;s Montreal Classification.\u003c/p\u003e\n\u003ch3\u003eActivating KIR2DS5 gene status and Prognostic Implications in PCD\u003c/h3\u003e\n\u003cp\u003eThe activating receptor KIR2DS5, expressed on natural killer (NK) cells, regulates immune responses through its short cytoplasmic domain binding TYRO proteins. This gene exhibits high polymorphism, with allele frequencies varying ethnically predominates in European populations, where mutations in critical extracellular residues (e.g., S111, F164) disrupt glycosylation, causing functional instability. Conversely, KIR2DS5 other mutation is frequent in African populations and confers protective effects via HLA-C2-specific binding. In CD, KIR2DS5 is a significant risk factor, with large-scale case-control studies confirming robust associations between its presence and increased CD susceptibility (OR\u0026thinsp;=\u0026thinsp;3.06, 95% CI: 2.36\u0026ndash;3.97; P\u0026thinsp;=\u0026thinsp;1.35 \u0026times; 10\u003csup\u003e\u0026minus;\u0026thinsp;17\u003c/sup\u003e)\u003csup\u003e[\u003cspan citationid=\"CR4\" class=\"CitationRef\"\u003e4\u003c/span\u003e]\u003c/sup\u003e. This risk persists across pediatric and adult Western European cohorts, suggesting a pathogenic role in disease progression. Mechanistically, KIR2DS5 enhances NK cell-mediated cytotoxicity and pro-inflammatory cytokine release (e.g., IFN-γ), exacerbating intestinal mucosal inflammation. Consequently, KIR2DS5 allelic genotyping may serve as a biomarker for risk stratification and prognostic assessment in high-susceptibility CD populations.The detection of a DNA band of the expected molecular weight was considered as the presence of the gene in the genomic DNA sample.The presence or absence of each activating KIR in all cases and controls was determined by using PCR and sequence-specific primers on their genomic DNA samples as described \u003csup\u003e[\u003cspan citationid=\"CR4\" class=\"CitationRef\"\u003e4\u003c/span\u003e]\u003c/sup\u003e.\u003c/p\u003e\u003cdiv id=\"Sec8\" class=\"Section2\"\u003e\u003ch2\u003eCovariate\u003c/h2\u003e\u003cp\u003eThe covariates in this study are: Gender (dichotomous), Age at diagnosis (continuous). Due to skewness, Age at diagnose is grouped into \u0026lt;\u0026thinsp;12 years, 12\u0026ndash;15 years, and \u0026gt;\u0026thinsp;15 years. Center/race represents ancestry: Montreal (French) and Ottawa (Caucasian). Disease location is classified as L1\u0026thinsp;\u0026plusmn;\u0026thinsp;L4, L2\u0026thinsp;\u0026plusmn;\u0026thinsp;L4, or L3\u0026thinsp;\u0026plusmn;\u0026thinsp;L4. Activating KIR gene status is categorized based on literature\u003csup\u003e[\u003cspan citationid=\"CR4\" class=\"CitationRef\"\u003e4\u003c/span\u003e]\u003c/sup\u003e.\u003c/p\u003e\u003cp\u003eFor the outcome variable, the study focuses on perianal disease. The original 3 - category variable (B1\u0026thinsp;\u0026plusmn;\u0026thinsp;p, B2\u0026thinsp;\u0026plusmn;\u0026thinsp;p, B3\u0026thinsp;\u0026plusmn;\u0026thinsp;p) is converted to a binary variable: non - perianal Crohn's disease vs Perianal Crohn\u0026rsquo;s disease.\u003c/p\u003e\u003c/div\u003e\n\u003ch3\u003eStatistical Analyses\u003c/h3\u003e\n\u003cp\u003eDescriptive analysis was performed on all participants, patient characteristics were described overall and stratified by group (outcome groups: isolated non-perianal Crohn's disease versus perianal Crohn's disease). Continuous data were expressed as median (interquartile range) based on normality distribution. Categorical variables were presented as percentages and analyzed using the Chi-square test.\u003c/p\u003e\u003cp\u003eBased on the adjustment models detailed in the study design, three hierarchical multivariable regression models were implemented to evaluate the association between KIR2DS5 and Crohn's disease (CD) risk while controlling for key covariates: Model 1 adjusted for core demographic variables including gender, age at diagnosis, and combined recruitment center/ancestral background (Montreal cohort: French ancestry; Ottawa cohort: Caucasian ancestry) to account for population stratification. Model 2 further adjusted for the covariates in Model 1 plus disease location (e.g., ileal, colonic, or ileocolonic involvement) to address potential confounding by CD phenotypic heterogeneity. Model 3 expanded adjustment to include covariates from Model 2 and the presence/absence of other functionally relevant KIR genes (KIR2DS1, KIR2DS2, KIR2DS3, KIR2DS4a, KIR2DS4b, and KIR3DS1), thereby isolating the independent effect of KIR2DS5 beyond linkage disequilibrium or epistatic interactions within the KIR gene cluster .\u003c/p\u003e\u003cp\u003ePropensity score matching (PSM) was used to adjust for confounders between the different groups. Using the estimated propensity scores as weights, an inverse probability weighting (IPW) model was used to generate a weighted cohort \u003csup\u003e[\u003cspan citationid=\"CR21\" class=\"CitationRef\"\u003e21\u003c/span\u003e]\u003c/sup\u003e.The probability of diagnosed with PCD was estimated using a logistic regression for each patient. We matched the two groups in a 1:1 ratio with a caliper width of 0.2. The standardized mean difference (SMD) was used to examine the degree of PSM.\u003c/p\u003e\u003cp\u003eThis tiered approach rigorously controlled for: Population-specific genetic background: Ancestry groups were stratified by recruitment center (Montreal/Ottawa) to mitigate population structure bias, consistent with established protocols for genetic association studies in admixed cohorts .Clinical heterogeneity: Inclusion of disease location (Montreal Classification) accounted for documented variations in disease behavior and severity .KIR-specific confounding: Adjustment for co-inherited activating KIR genes (KIR2DS1-3, KIR2DS4a/b, KIR3DS1) addressed haplotype-driven effects, as KIR genes exhibit strong linkage disequilibrium on chromosome 19q13.4 .The models employed multivariable logistic regression with statistical significance defined as P\u0026thinsp;\u0026lt;\u0026thinsp;0.05 (two-tailed), aligning with methodologies in prior KIR-CD association studies .\u003c/p\u003e\u003cp\u003eThe statistical analyses were performed using FreeStatistics (version 2.1.1), a software package designed with user-friendly interfaces that facilitate common analyses and data visualization. This software relies on R as its core statistical engine, while its graphical user interface (GUI) is built using Python. Most analyses can be completed with just a few clicks, enhancing efficiency for reproducible analysis and interactive computing. FreeStatistics is developed by FreeClinical Medical Technology Co., Ltd, based in Beijing, China, and can be accessed at \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttp://www.clinicalscientists.cn/freestatistics/\u003c/span\u003e\u003cspan address=\"http://www.clinicalscientists.cn/freestatistics/\" targettype=\"URL\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e.\u003c/p\u003e"},{"header":"Results","content":"\u003cdiv id=\"Sec11\" class=\"Section2\"\u003e\u003ch2\u003eParticipants and Demographic Characteristics\u003c/h2\u003e\u003cp\u003eIn the study of Crohn's disease (CD) cohorts from Ottawa and Montreal, a total of 1021 cases were initially identified. After excluding 565 control cases, 456 cases remained. Further exclusions were made due to missing data of age at diagnosis and gender (170 cases), disease location and behavior (99 cases), resulting in a final cohort of 187 cases (Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003e). These cases were categorized into non-perianal CD (n\u0026thinsp;=\u0026thinsp;146) and perianal CD (n\u0026thinsp;=\u0026thinsp;41) groups. The demographic and clinical characteristics of these groups are summarized in Table\u0026nbsp;\u003cspan refid=\"Tab1\" class=\"InternalRef\"\u003e1\u003c/span\u003e. To investigate the distribution of present of activating KIR2DS5 gene in patients with Crohn's disease (CD) and its correlation with clinical characteristics.A total of 187 CD patients were included, among whom 76 did not carry the activating KIR2DS5 gene and 111 did. The results showed that the median age at diagnosis was 12.8 years, with no significant difference in the age at diagnosis between patients with and without the activating KIR2DS5 gene present (P\u0026thinsp;=\u0026thinsp;0.597). In terms of age stratification, there was no significant difference in the proportion of patients with and without the activating KIR2DS5 gene in the 2.5\u0026ndash;11 years, 12\u0026ndash;15 years, and \u0026gt;\u0026thinsp;15 years age groups (P\u0026thinsp;=\u0026thinsp;0.417). Regarding the distribution of centers and races, there was a significant difference in the proportion of patients with the activating KIR2DS5 gene between Montreal (French ancestry) and Ottawa (Caucasian ancestry) (P\u0026thinsp;\u0026lt;\u0026thinsp;0.001), with a higher proportion of activating KIR2DS5 status carriers in Montreal. The proportion of male and female patients with and without the activating KIR2DS5 status showed no significant difference (P\u0026thinsp;=\u0026thinsp;0.235). For other KIR genes, such as KIR2DS1, KIR2DS2, KIR3DS3, KIR2DS4a, KIR2DS4b, and KIR3DS1, there was no significant difference in their distribution between the two groups (P\u0026thinsp;\u0026gt;\u0026thinsp;0.05), except for KIR2DS5, which was significantly different (P\u0026thinsp;\u0026lt;\u0026thinsp;0.001), in patients without the activating KIR2DS5 gene. In terms of disease behavior and location, there was no significant difference in the proportion of patients with and without the activating KIR2DS5 gene status among those with non-perianal and perianal Crohn's disease (P\u0026thinsp;=\u0026thinsp;0.187), as well as among those with different disease locations (L1\u0026thinsp;\u0026plusmn;\u0026thinsp;L4, L2\u0026thinsp;\u0026plusmn;\u0026thinsp;L4, L3\u0026thinsp;\u0026plusmn;\u0026thinsp;L4) (P\u0026thinsp;=\u0026thinsp;0.327).\u003c/p\u003e\u003cp\u003e\u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"Yes\" id=\"Tab1\" border=\"1\"\u003e\u003ccaption language=\"En\"\u003e\u003cdiv class=\"CaptionNumber\"\u003eTable 1\u003c/div\u003e\u003cdiv class=\"CaptionContent\"\u003e\u003cp\u003e, Association Analysis of whether activating KIR2DS5 Gene present or not and Clinical Features in Patients with Crohn's Disease.\u003c/p\u003e\u003c/div\u003e\u003c/caption\u003e\u003ccolgroup cols=\"5\"\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e\u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c3\" colnum=\"3\"\u003e\u003c/div\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c4\" colnum=\"4\"\u003e\u003c/div\u003e\u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c5\" colnum=\"5\"\u003e\u003c/div\u003e\u003cthead\u003e\u003ctr\u003e\u003cth align=\"left\" colname=\"c1\"\u003e\u003cp\u003eVariables\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c2\"\u003e\u003cp\u003eTotal (n\u0026thinsp;=\u0026thinsp;187)\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c3\"\u003e\u003cp\u003eActivating KIR2DS5 absent (n\u0026thinsp;=\u0026thinsp;76)\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c4\"\u003e\u003cp\u003eActivating KIR2DS5 present (n\u0026thinsp;=\u0026thinsp;111)\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c5\"\u003e\u003cp\u003e\u003cem\u003eP\u003c/em\u003e value\u003c/p\u003e\u003c/th\u003e\u003c/tr\u003e\u003c/thead\u003e\u003ctbody\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eAge at diagnose, Median (IQR)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e\u003cp\u003e12.8 (10.6, 14.6)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e12.8 (10.9, 14.0)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e12.8 (10.5, 14.7)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e\u003cp\u003e0.597\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eAge, n (%)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e\u003cp\u003e0.417\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e2.5\u0026thinsp;~\u0026thinsp;11y\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e\u003cp\u003e73 (39.0)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e34 (44.7)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e39 (35.1)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u0026nbsp;\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e12\u0026thinsp;~\u0026thinsp;15y\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e\u003cp\u003e73 (39.0)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e27 (35.5)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e46 (41.4)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u0026nbsp;\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e\u0026gt;\u0026thinsp;15y\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e\u003cp\u003e41 (21.9)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e15 (19.7)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e26 (23.4)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u0026nbsp;\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eCenter/race, n (%)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e\u003cp\u003e\u0026lt;\u0026thinsp;0.001\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eMontreal(French ancestry)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e\u003cp\u003e95 (50.8)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e26 (34.2)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e69 (62.2)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u0026nbsp;\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eOttawa(Caucasian ancestry)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e\u003cp\u003e92 (49.2)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e50 (65.8)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e42 (37.8)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u0026nbsp;\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eGender, n (%)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e\u003cp\u003e0.235\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eFemale\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e\u003cp\u003e91 (48.7)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e33 (43.4)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e58 (52.3)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u0026nbsp;\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eMale\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e\u003cp\u003e96 (51.3)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e43 (56.6)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e53 (47.7)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u0026nbsp;\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eKIR2DS1, n (%)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e\u003cp\u003e0.81\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eAbsent\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e\u003cp\u003e46 (24.6)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e18 (23.7)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e28 (25.2)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u0026nbsp;\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003ePresent\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e\u003cp\u003e141 (75.4)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e58 (76.3)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e83 (74.8)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u0026nbsp;\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eKIR2DS2, n (%)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e\u003cp\u003e0.517\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eAbsent\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e\u003cp\u003e49 (26.2)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e18 (23.7)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e31 (27.9)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u0026nbsp;\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003ePresent\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e\u003cp\u003e138 (73.8)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e58 (76.3)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e80 (72.1)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u0026nbsp;\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eKIR3DS3, n (%)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e\u003cp\u003e0.944\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eAbsent\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e\u003cp\u003e88 (47.1)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e36 (47.4)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e52 (46.8)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u0026nbsp;\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003ePresent\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e\u003cp\u003e99 (52.9)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e40 (52.6)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e59 (53.2)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u0026nbsp;\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eKIR2DS4a, n (%)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e\u003cp\u003e0.713\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eAbsent\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e\u003cp\u003e49 (26.2)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e21 (27.6)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e28 (25.2)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u0026nbsp;\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003ePresent\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e\u003cp\u003e138 (73.8)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e55 (72.4)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e83 (74.8)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u0026nbsp;\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eKIR2DS4b, n (%)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e\u003cp\u003e0.713\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eAbsent\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e\u003cp\u003e49 (26.2)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e21 (27.6)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e28 (25.2)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u0026nbsp;\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003ePresent\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e\u003cp\u003e138 (73.8)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e55 (72.4)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e83 (74.8)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u0026nbsp;\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eKIR2DS5, n (%)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e\u003cp\u003e\u0026lt;\u0026thinsp;0.001\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eAbsent\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e\u003cp\u003e76 (40.6)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e76 (100)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e0 (0)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u0026nbsp;\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003ePresent\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e\u003cp\u003e111 (59.4)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e0 (0)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e111 (100)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u0026nbsp;\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eKIR3DS1, n (%)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e\u003cp\u003e0.053\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eAbsent\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e\u003cp\u003e73 (39.0)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e36 (47.4)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e37 (33.3)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u0026nbsp;\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003ePresent\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e\u003cp\u003e114 (61.0)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e40 (52.6)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e74 (66.7)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u0026nbsp;\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eDisease behavior, n (%)\u0026dagger;\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e\u003cp\u003e0.187\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003enon-perianal Crohn's disease\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e\u003cp\u003e146 (78.1)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e63 (82.9)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e83 (74.8)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u0026nbsp;\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003ePerianal Crohn\u0026rsquo;s disease\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e\u003cp\u003e41 (21.9)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e13 (17.1)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e28 (25.2)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u0026nbsp;\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eDisease location, n (%)\u0026dagger;\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e\u003cp\u003e0.327\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eL1\u0026thinsp;\u0026plusmn;\u0026thinsp;L4\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e\u003cp\u003e38 (20.3)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e19 (25)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e19 (17.1)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u0026nbsp;\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eL2\u0026thinsp;\u0026plusmn;\u0026thinsp;L4\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e\u003cp\u003e47 (25.1)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e16 (21.1)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e31 (27.9)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u0026nbsp;\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eL3\u0026thinsp;\u0026plusmn;\u0026thinsp;L4\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e\u003cp\u003e102 (54.5)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e41 (53.9)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e61 (55)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u0026nbsp;\u003c/td\u003e\u003c/tr\u003e\u003c/tbody\u003e\u003c/colgroup\u003e\u003ctfoot\u003e\u003ctr\u003e\u003ctd colspan=\"5\"\u003e\u0026dagger;Classification based on the WGO\u0026rsquo;s Montreal Classification. The age at diagnosis cut-off for study inclusion was 16 years in Ottawa and 20 years in Montreal. Four patients had disease restricted to either only the upper tract or anal region and for three patients the location could not be adequately classified. For two patients, the disease behaviour at diagnosis was not clear. The percentages may not add up due to rounding.\u003c/td\u003e\u003c/tr\u003e\u003c/tfoot\u003e\u003c/table\u003e\u003c/div\u003e\u003c/p\u003e\u003c/div\u003e\u003cdiv id=\"Sec12\" class=\"Section2\"\u003e\u003ch2\u003eAssociations between present of activating KIR2DS5 and Perianal Crohn's disease (PCD)\u003c/h2\u003e\u003cp\u003eIn the association analysis, various statistical models were employed to assess the association between the activating KIR2DS5 status and the risk of Perianal Crohn's disease (PCD), adjusting for potential confounding factors. The unmatched crude model indicated a potential association with an odds ratio (OR) of 1.63 (95% CI: 0.78\u0026ndash;3.41, P\u0026thinsp;=\u0026thinsp;0.19), which was not statistically significant(Table\u0026nbsp;\u003cspan refid=\"Tab2\" class=\"InternalRef\"\u003e2\u003c/span\u003e). However, after adjusting for multiple variables in the multivariable model, refer to activating KIR2DS5 absent groups, the odds ratio in activating KIR2DS5 present groups increased to 2.52 (95% CI: 1.1\u0026ndash;5.76, P\u0026thinsp;=\u0026thinsp;0.029), suggesting a statistically significant association(Table\u0026nbsp;\u003cspan refid=\"Tab2\" class=\"InternalRef\"\u003e2\u003c/span\u003e). Propensity score adjustment, which balances known confounding factors, yielded an OR of 2.44 (95% CI: 1.08\u0026ndash;5.52, P\u0026thinsp;=\u0026thinsp;0.032), similar to the multivariable adjusted model(Table\u0026nbsp;\u003cspan refid=\"Tab2\" class=\"InternalRef\"\u003e2\u003c/span\u003e). The inverse probability of treatment weighting (IPTW) model, which assigns weights to balance differences between groups, also showed a significant association with an OR of 2.53 (95% CI: 1.16\u0026ndash;5.54, P\u0026thinsp;=\u0026thinsp;0.02)(Table\u0026nbsp;\u003cspan refid=\"Tab3\" class=\"InternalRef\"\u003e3\u003c/span\u003e).\u003c/p\u003e\u003cp\u003e\u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"Yes\" id=\"Tab2\" border=\"1\"\u003e\u003ccaption language=\"En\"\u003e\u003cdiv class=\"CaptionNumber\"\u003eTable 2\u003c/div\u003e\u003cdiv class=\"CaptionContent\"\u003e\u003cp\u003eAssociation between the risk of Perianal Crohn\u0026rsquo;s disease and activating KIR2DS5 present or not.\u003c/p\u003e\u003c/div\u003e\u003c/caption\u003e\u003ccolgroup cols=\"9\"\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c3\" colnum=\"3\"\u003e\u003c/div\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c4\" colnum=\"4\"\u003e\u003c/div\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c5\" colnum=\"5\"\u003e\u003c/div\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c6\" colnum=\"6\"\u003e\u003c/div\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c7\" colnum=\"7\"\u003e\u003c/div\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c8\" colnum=\"8\"\u003e\u003c/div\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c9\" colnum=\"9\"\u003e\u003c/div\u003e\u003cthead\u003e\u003ctr\u003e\u003cth align=\"left\" colname=\"c1\"\u003e\u0026nbsp;\u003c/th\u003e\u003cth align=\"left\" colname=\"c2\"\u003e\u0026nbsp;\u003c/th\u003e\u003cth align=\"left\" colname=\"c3\"\u003e\u0026nbsp;\u003c/th\u003e\u003cth align=\"left\" colspan=\"2\" nameend=\"c5\" namest=\"c4\"\u003e\u003cp\u003eModel1\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colspan=\"2\" nameend=\"c7\" namest=\"c6\"\u003e\u003cp\u003eModel2\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colspan=\"2\" nameend=\"c9\" namest=\"c8\"\u003e\u003cp\u003eModel3\u003c/p\u003e\u003c/th\u003e\u003c/tr\u003e\u003c/thead\u003e\u003ctbody\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eKIR2DS5\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003en\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003eEvent(%)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003eOR (95%CI)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e\u003cem\u003eP value\u003c/em\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\"\u003e\u003cp\u003eOR (95%CI)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c7\"\u003e\u003cp\u003e\u003cem\u003eP value\u003c/em\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c8\"\u003e\u003cp\u003eOR (95%CI)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c9\"\u003e\u003cp\u003e\u003cem\u003eP value\u003c/em\u003e\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eAbsent\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e76\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e13 (17.1)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e1(Ref)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\"\u003e\u003cp\u003e1(Ref)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c7\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"left\" colname=\"c8\"\u003e\u003cp\u003e1(Ref)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c9\"\u003e\u0026nbsp;\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003ePresent\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e111\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e28 (25.2)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e2.44 (1.08\u0026thinsp;~\u0026thinsp;5.49)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e0.032\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\"\u003e\u003cp\u003e2.4 (1.06\u0026thinsp;~\u0026thinsp;5.41)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c7\"\u003e\u003cp\u003e0.035\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c8\"\u003e\u003cp\u003e2.49 (1.09\u0026thinsp;~\u0026thinsp;5.69)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c9\"\u003e\u003cp\u003e0.031\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003c/tbody\u003e\u003c/colgroup\u003e\u003ctfoot\u003e\u003ctr\u003e\u003ctd colspan=\"9\"\u003e\u0026bull;Model 1: Adjusts for gender, age at diagnosis and center/race.\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd colspan=\"9\"\u003e\u0026bull;Model 2: Adjusts for the covariates in Model 1 plus disease location.\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd colspan=\"9\"\u003e\u0026bull;Model 3: Adjusts for the covariates in Model 2 plus the presence of other KIR genes (KIR2DS1, KIR2DS2, KIR2DS3, KIR2DS4a, KIR2DS4b, KIR3DS1).\u003c/td\u003e\u003c/tr\u003e\u003c/tfoot\u003e\u003c/table\u003e\u003c/div\u003e\u003c/p\u003e\u003cp\u003e\u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"Yes\" id=\"Tab3\" border=\"1\"\u003e\u003ccaption language=\"En\"\u003e\u003cdiv class=\"CaptionNumber\"\u003eTable 3\u003c/div\u003e\u003cdiv class=\"CaptionContent\"\u003e\u003cp\u003eSensitivity validation of the association between activated KIR2DS5 and perianal Crohn\u0026rsquo;s disease lesions using propensity-score-matched analysis\u003c/p\u003e\u003c/div\u003e\u003c/caption\u003e\u003ccolgroup cols=\"4\"\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e\u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c3\" colnum=\"3\"\u003e\u003c/div\u003e\u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c4\" colnum=\"4\"\u003e\u003c/div\u003e\u003cthead\u003e\u003ctr\u003e\u003cth align=\"left\" colname=\"c1\"\u003e\u003cp\u003eModels\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c2\"\u003e\u003cp\u003eItem1\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c3\"\u003e\u003cp\u003eOR (95%CI)\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c4\"\u003e\u003cp\u003e\u003cem\u003eP value\u003c/em\u003e\u003c/p\u003e\u003c/th\u003e\u003c/tr\u003e\u003c/thead\u003e\u003ctbody\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eUnmatched.crude\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003eActivating KIR2DS5: Present vs Absent\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e\u003cp\u003e1.63 (0.78\u0026thinsp;~\u0026thinsp;3.41)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e\u003cp\u003e0.19\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eMultivariable.adjusted\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003eActivating KIR2DS5: Present vs Absent\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e\u003cp\u003e2.52 (1.1\u0026thinsp;~\u0026thinsp;5.76)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e\u003cp\u003e0.029\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003ePropensityScore.adjusted\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003eActivating KIR2DS5: Present vs Absent\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e\u003cp\u003e2.44 (1.08\u0026thinsp;~\u0026thinsp;5.52)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e\u003cp\u003e0.032\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eWeighted.IPTW\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003eActivating KIR2DS5: Present vs Absent\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e\u003cp\u003e2.53 (1.16\u0026thinsp;~\u0026thinsp;5.54)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e\u003cp\u003e0.02\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003c/tbody\u003e\u003c/colgroup\u003e\u003ctfoot\u003e\u003ctr\u003e\u003ctd colspan=\"4\"\u003eThe analysis results of the variable KIR2DS5 (Present vs Absent) under different statistical models, including the odds ratio (OR), 95% confidence interval (95% CI), and P-value. These models range from the unmatched crude model to those adjusted by various propensity score matching and weighting methods.\u003c/td\u003e\u003c/tr\u003e\u003c/tfoot\u003e\u003c/table\u003e\u003c/div\u003e\u003c/p\u003e\u003c/div\u003e\u003cdiv id=\"Sec13\" class=\"Section2\"\u003e\u003ch2\u003eSubgroup Analyses\u003c/h2\u003e\u003cp\u003eIn the sensitivity subgroup analysis, the impact of the activating KIR2DS5 gene status on the risk of Perianal Crohn's disease (PCD) was assessed across various subgroups after adjusting for confounding factors. The results, as presented in Supp.Table\u0026nbsp;\u003cspan refid=\"Tab1\" class=\"InternalRef\"\u003e1\u003c/span\u003e and the corresponding forest plot(Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003e), indicate stability across all subgroups(Supp.Table\u0026nbsp;\u003cspan refid=\"Tab1\" class=\"InternalRef\"\u003e1\u003c/span\u003e). Notably, the subgroup of different ancestral origins showed a P.for.interaction of 0.07, suggesting a potential interaction effect(Supp.Table\u0026nbsp;\u003cspan refid=\"Tab1\" class=\"InternalRef\"\u003e1\u003c/span\u003e,Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003e), but the \u003cem\u003eP.value\u003c/em\u003e was not significant, maybe due to not so much cases, we need to colected more case in the future. Specifically, within the Montreal cohort, children of French ancestry with the SNP were found to be more susceptible to PCD, highlighting the presence of an interaction(Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003e). This finding underscores the importance of considering genetic ancestry in the context of present of activating KIR2DS5 and PCD risk(Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003e).\u003c/p\u003e\u003cp\u003e\u003c/p\u003e\u003c/div\u003e"},{"header":"Discussion","content":"\u003cp\u003ePerianal Crohn\u0026rsquo;s disease (PCD) represents a significant complication of Crohn\u0026rsquo;s disease, characterized by various perianal manifestations, including perianal fistulas, abscesses, and skin tags. The multifaceted nature of PCD, coupled with its association with serious outcomes like anal cancer, underscores the urgent need for comprehensive research to enhance early diagnosis and effective management strategies for affected individuals\u003csup\u003e[\u003cspan citationid=\"CR7\" class=\"CitationRef\"\u003e7\u003c/span\u003e, \u003cspan citationid=\"CR8\" class=\"CitationRef\"\u003e8\u003c/span\u003e]\u003c/sup\u003e.\u003c/p\u003e\u003cp\u003eIn this study, we aimed to elucidate the relationship between killer cell immunoglobulin-like receptor (KIR) gene activating status and the risk of developing PCD. By analyzing clinical data from a cohort of 1,021 Crohn\u0026rsquo;s disease patients, ultimately narrowing our focus to 187 subjects, we sought to identify significant associations that may inform clinical practice. From a rigorously phenotyped paediatric Crohn\u0026rsquo;s disease (CD) cohort (n\u0026thinsp;=\u0026thinsp;187, median age at diagnosis 12.8 years) derived from Ottawa (Caucasian) and Montr\u0026eacute;al (French-Canadian) centres, carriage of the activating KIR2DS5 status was markedly enriched in the Montr\u0026eacute;al population (P\u0026thinsp;\u0026lt;\u0026thinsp;0.001). Multivariable logistic regression, propensity-score adjustment and inverse-probability-of-treatment weighting converged on a consistent and independent association between KIR2DS5 presence and perianal CD (adjusted OR 2.52, 95% CI 1.10\u0026ndash;5.76, P\u0026thinsp;=\u0026thinsp;0.029; OR 2.44, 1.08\u0026ndash;5.52, P\u0026thinsp;=\u0026thinsp;0.032; and OR 2.53, 1.16\u0026ndash;5.54, P\u0026thinsp;=\u0026thinsp;0.020, respectively), whereas no heterogeneity was observed across age strata, sex, or conventional Montreal classifications. Exploratory ancestry-stratified analyses revealed a trend toward stronger effect modification in children of French ancestry (Pinteraction\u0026thinsp;=\u0026thinsp;0.07), underscoring the potential contribution of population-specific genetic background to KIR2DS5-mediated susceptibility to perianal CD.The findings indicate a notable divergence in KIR gene expression among patients with PCD, suggesting a potential role of these genes in modulating the disease\u0026rsquo;s pathogenesis. This discussion will delve into the implications of our findings, underscoring the importance of understanding the genetic predispositions that contribute to the clinical manifestations of PCD\u003csup\u003e[\u003cspan citationid=\"CR6\" class=\"CitationRef\"\u003e6\u003c/span\u003e, \u003cspan citationid=\"CR22\" class=\"CitationRef\"\u003e22\u003c/span\u003e]\u003c/sup\u003e.\u003c/p\u003e\u003cp\u003eThe association of activating KIR genes with the risk of perianal Crohn\u0026rsquo;s disease (PCD) presents promising implications for understanding the pathogenesis of this debilitating condition. Our findings indicate significant differences in KIR gene phenotypes among patients with PCD, particularly in the frequency of specific KIR genotypes. This suggests that KIR genes may play a pivotal role in modulating immune responses, potentially influencing the development and severity of Crohn\u0026rsquo;s disease manifestations. Previous studies have highlighted the importance of KIR and HLA interactions in various autoimmune diseases, suggesting a similar mechanism may underpin PCD. Notably, the presence of certain KIR genotypes has been correlated with autoimmune conditions, emphasizing their potential as biomarkers for assessing PCD risk[8]. Further investigation into the mechanisms through which KIR genes affect immune responses could pave the way for targeted therapeutic strategies aimed at mitigating the impact of PCD.\u003c/p\u003e\u003cp\u003eThe diverse clinical manifestations of PCD, including anal fissures and perianal abscesses, complicate its early diagnosis and management. Our analysis revealed that patients with PCD frequently present with a spectrum of symptoms, which may contribute to diagnostic delays. The variability in clinical presentation underlines the necessity for clinicians to maintain a high index of suspicion, particularly in pediatric populations where symptoms may be misattributed to less severe conditions. Early intervention has been shown to significantly influence disease progression and improve patient outcomes, highlighting the critical importance of recognizing and addressing these symptoms promptly\u003csup\u003e[\u003cspan citationid=\"CR3\" class=\"CitationRef\"\u003e3\u003c/span\u003e]\u003c/sup\u003e. The robust epidemiologic association between activating KIR2DS5 and paediatric perianal Crohn\u0026rsquo;s disease (PCD) suggests a mechanistic axis in which ligand\u0026ndash;receptor engagement on mucosal natural killer (NK) and cytotoxic T cells lowers the activation threshold for type-1 cytokine release, thereby amplifying a TH1/TH17-biased inflammatory loop within the densely innervated anoderm. KIR2DS5 recognises HLA-C2\u003csup\u003e[\u003cspan citationid=\"CR4\" class=\"CitationRef\"\u003e4\u003c/span\u003e, \u003cspan citationid=\"CR5\" class=\"CitationRef\"\u003e5\u003c/span\u003e, \u003cspan additionalcitationids=\"CR24\" citationid=\"CR23\" class=\"CitationRef\"\u003e23\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR25\" class=\"CitationRef\"\u003e25\u003c/span\u003e]\u003c/sup\u003e and possibly non-classical MHC-I molecules that are up-regulated on stressed colonic epithelium; its activating ITAM-bearing tail recruits ZAP70/SYK kinases to trigger perforin/granzyme secretion and IFN-γ production\u003csup\u003e[\u003cspan citationid=\"CR26\" class=\"CitationRef\"\u003e26\u003c/span\u003e]\u003c/sup\u003e. In tissue niches already compromised by epithelial breach, this exaggerated effector response may accelerate fistulising cascades driven by IL-23\u0026ndash;responsive γδ T cells and neutrophil extracellular traps. Importantly, the absence of association between PCD and other activating KIRs (KIR2DS1, 2DS2, 2DS4a/b, 3DS1) implies that these paralogues either engage low-affinity ligands under inflammatory conditions or are epigenetically silenced in the rectal mucosa. Furthermore, compensatory inhibitory KIR-KIR ligand interactions (e.g., KIR2DL3\u0026ndash;HLA-C1) may counterbalance activating signals, explaining the neutral effect of KIR2DS4 deletions or KIR3DS1 polymorphisms on PCD penetrance. Collectively, the data delineate a gene-dosage model in which KIR2DS5\u003csup\u003e[\u003cspan citationid=\"CR27\" class=\"CitationRef\"\u003e27\u003c/span\u003e]\u003c/sup\u003e emerges as the principal activating KIR that licences NK-mediated immunopathology in perianal Crohn\u0026rsquo;s disease, while other activating KIR variants remain mechanistically silent or are physiologically restrained by inhibitory checkpoints.\u003c/p\u003e\u003cp\u003eThe design of our cohort study effectively elucidates the relationship between KIR gene variation and PCD risk. By ensuring a representative sample and controlling for confounding variables, we bolster the reliability of our findings. This methodology allows for a clearer interpretation of how specific genetic markers may predispose individuals to PCD, potentially guiding future research and clinical practice. The robustness of the case-control design enhances its applicability in identifying high-risk populations, which is crucial for early diagnosis and intervention strategies\u003csup\u003e[\u003cspan citationid=\"CR9\" class=\"CitationRef\"\u003e9\u003c/span\u003e]\u003c/sup\u003e. Future studies could further refine these methodologies to explore additional genetic and environmental factors influencing PCD risk.\u003c/p\u003e\u003cp\u003eThe demographic diversity of our study population strengthens the generalizability of our results. By including individuals from varied ethnic backgrounds, we can better understand how genetic factors may differ across populations and contribute to PCD prevalence. This diversity highlights the need for further research into the genetic epidemiology of PCD, particularly in underrepresented groups. Understanding ethnic variations in KIR gene distribution could illuminate differences in disease susceptibility and inform culturally competent clinical practices. Comparative studies across diverse populations will be essential to delineate the role of genetic factors in the pathogenesis of PCD and other related autoimmune diseases\u003csup\u003e[\u003cspan citationid=\"CR28\" class=\"CitationRef\"\u003e28\u003c/span\u003e]\u003c/sup\u003e.\u003c/p\u003e\u003cp\u003eIn summary, our research underscores the potential of KIR genes as critical players in the etiology of PCD. The findings not only enhance our understanding of the disease but also open new avenues for targeted interventions and personalized treatment strategies. Continued exploration of KIR gene interactions and their implications for immune regulation will be crucial for developing effective therapeutic approaches for PCD and similar autoimmune conditions. Future studies should focus on the translational potential of these findings, aiming to integrate genetic insights into clinical practice and improve patient outcomes\u003csup\u003e[\u003cspan citationid=\"CR6\" class=\"CitationRef\"\u003e6\u003c/span\u003e]\u003c/sup\u003e.\u003c/p\u003e\u003cp\u003eThe limitations of this study include a sample size only 187 cases were categorized into two groups: non-perianal Crohn's disease (n\u0026thinsp;=\u0026thinsp;146) and perianal Crohn's disease (n\u0026thinsp;=\u0026thinsp;41), which may affect the generalizability of the findings. Although the cohort was derived from diverse ethnic backgrounds, the limited number of cases may restrict the robustness of the conclusions drawn regarding the association between KIR genes and perianal Crohn\u0026rsquo;s disease. Additionally, the lack of clinical validation analysis may hinder the ability to translate these findings into practical applications. Variability in the data collection process and potential inter-study differences could also introduce biases that influence the results. Therefore, further research with larger cohorts and stringent validation methodologies is critical to substantiate the observed associations.\u003c/p\u003e"},{"header":"Conclusion","content":"\u003cp\u003eIn conclusion, this study highlights the significant association between KIR genes and perianal Crohn\u0026rsquo;s disease, underscoring the importance of diverse participant samples in identifying risk factors. The findings pave the way for future investigations aimed at elucidating the roles of KIR genes and their interactions with other immune-related genes. Such research is essential for the development of personalized treatment strategies and innovative interventions for perianal Crohn\u0026rsquo;s disease, ultimately improving patient outcomes.\u003c/p\u003e"},{"header":"Declarations","content":"\u003cp\u003e\u003cstrong\u003eAcknowledgments\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eWe appreciate Dr. Jie Liu of the Department of Vascular and Endovascular Surgery, Chinese PLA General Hospital \u0026amp; Physician-Scientist Center of China for statistics, study deign consultations and editing the manuscript.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eStatement of Ethics\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eEthical approval and consent were not required as this study was based on publicly available de-identified data.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eConflict of Interest Statement\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe remaining authors declare that they have no conflict of interest.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eFunding Sources\u0026nbsp;\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eLiangping Cheng, Talent Introduction Startup Fund, Grant ID:4000036\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eAuthor Contributions\u0026nbsp;\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eZhongsu Yu: conceptualization, formal analysis, and writing-original draft.Huajian Hu: \u0026nbsp;formal analysis and writing-original draft. Liangping Cheng: writing-review and editing-and project administration. All authors contributed to and approved the final manuscript.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eData Availability Statement\u0026nbsp;\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eRaw relevant data are deposited on Dryad. (https://datadryad.org/dataset/doi:10.5061/dryad.1q5q65g). Further inquiries can be directed to the corresponding author.\u003c/p\u003e"},{"header":"References","content":"\u003col\u003e\u003cli\u003e\u003cspan\u003eParian, A. M. et al. Management of perianal crohn\u0026rsquo;s disease[J]. \u003cem\u003eAm. J. 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Bowel Dis.\u003c/em\u003e \u003cb\u003e15\u003c/b\u003e (4), 501\u0026ndash;507 (2009).\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eAmre, D. K. et al. Association between genetic variants in the IL-23R gene and early-onset crohn\u0026rsquo;s disease: results from a case-control and family-based study among canadian children[J]. \u003cem\u003eAm. J. Gastroenterol.\u003c/em\u003e \u003cb\u003e103\u003c/b\u003e (3), 615\u0026ndash;620 (2008).\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eAmre, D. K. et al. \u003cem\u003eInterleukin 10 (IL-10) gene variants and susceptibility for paediatric onset crohn\u0026rsquo;s disease[J]\u003c/em\u003e Vol. 29, 1025\u0026ndash;1031 (Alimentary Pharmacology \u0026amp; Therapeutics, 2009). 9.\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eAmre, D. K. et al. \u003cem\u003eSusceptibility loci reported in genome-wide association studies are associated with crohn\u0026rsquo;s disease in canadian children[J]\u003c/em\u003e Vol. 31, 1186\u0026ndash;1191 (Alimentary Pharmacology \u0026amp; Therapeutics, 2010). 11.\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eZhiwei, L., Feihu, Y. \u0026amp; Chunfang, G. Advances in surgical diagnosis and treatment of perianal fistulizing Crohn\u0026rsquo;s disease[J]. \u003cem\u003eJ. Colorectal Anal. Surg.\u003c/em\u003e \u003cb\u003e31\u003c/b\u003e (1), 82\u0026ndash;88 (2025).\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eSordo-Mejia, R. \u0026amp; Gaertner, W. B. Multidisciplinary and evidence-based management of fistulizing perianal crohn\u0026rsquo;s disease[J]. \u003cem\u003eWorld J. Gastrointest. Pathophysiology\u003c/em\u003e. \u003cb\u003e5\u003c/b\u003e (3), 239\u0026ndash;251 (2014).\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eGuzela, V. 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Association of KIR2DL2 gene with anti-cyclic citrullinated protein antibodies for serodiagnosis in rheumatoid arthritis[J]. \u003cem\u003eMedicina\u003c/em\u003e \u003cb\u003e79\u003c/b\u003e (3), 161\u0026ndash;166 (2019).\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eStewart, C. A., Laugier-Anfossi, F., V\u0026eacute;ly, F. \u0026amp; 等 Recognition of peptide-MHC class I complexes by activating killer immunoglobulin-like receptors[J]. \u003cem\u003eProc. Natl. Acad. Sci. U.S.A.\u003c/em\u003e \u003cb\u003e102\u003c/b\u003e (37), 13224\u0026ndash;13229 (2005).\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eHollenbach, J. A. et al. Susceptibility to crohn\u0026rsquo;s disease is mediated by KIR2DL2/KIR2DL3 heterozygosity and the HLA-C ligand[J]. \u003cem\u003eImmunogenetics\u003c/em\u003e \u003cb\u003e61\u003c/b\u003e (10), 663\u0026ndash;671 (2009).\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eSteiner, N. K. et al. 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The role of killer-cell immunoglobulin-like receptor (KIR) genes in susceptibility to inflammatory bowel disease: systematic review and meta-analysis[J]. \u003cem\u003eInflamm. Research: Official J. Eur. Histamine Res. Soc. \u0026hellip; et Al]\u003c/em\u003e. \u003cb\u003e67\u003c/b\u003e (9), 727\u0026ndash;736 (2018).\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eRitari, J. et al. Disease associations of natural killer (NK) cell KIR gene content variation in 352,783 finns[J]. \u003cem\u003eHum. Immunol.\u003c/em\u003e \u003cb\u003e85\u003c/b\u003e (6), 111177 (2024).\u003c/span\u003e\u003c/li\u003e\u003c/ol\u003e"}],"fulltextSource":"","fullText":"","funders":[],"hasAdminPriorityOnWorkflow":false,"hasManuscriptDocX":true,"hasOptedInToPreprint":true,"hasPassedJournalQc":"","hasAnyPriority":false,"hideJournal":false,"highlight":"","institution":"","isAcceptedByJournal":false,"isAuthorSuppliedPdf":false,"isDeskRejected":"","isHiddenFromSearch":false,"isInQc":false,"isInWorkflow":false,"isPdf":false,"isPdfUpToDate":true,"isWithdrawnOrRetracted":false,"journal":{"display":true,"email":"[email protected]","identity":"scientific-reports","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":false,"externalIdentity":"scirep","sideBox":"Learn more about [Scientific Reports](http://www.nature.com/srep/)","snPcode":"","submissionUrl":"","title":"Scientific Reports","twitterHandle":"","acdcEnabled":true,"dfaEnabled":true,"editorialSystem":"stoa","reportingPortfolio":"Scientific Reports","inReviewEnabled":true,"inReviewRevisionsEnabled":true},"keywords":"KIR2DS5, Perianal Crohn’s Disease (PCD), Pediatric Crohn’s Disease, Genetic Risk Factors, Cohort Study","lastPublishedDoi":"10.21203/rs.3.rs-7953845/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-7953845/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"\u003cp\u003e\u003cstrong\u003eObjective\u003c/strong\u003e: Perianal Crohn’s disease (PCD) is a severe complication of Crohn’s disease (CD) that significantly impacts the quality of life in pediatric patients. This study aims to investigate the clinical risk factors associated with PCD, particularly focusing on the role of Killer cell immunoglobulin-like receptor (KIR) gene present or not in a Canadian pediatric cohort.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eMethods\u003c/strong\u003e: Data were collected from 1,021 individuals diagnosed with CD in Ottawa and Montreal, Canada. The study employed a cohort design to assess the association between KIR gene polymorphisms and the risk of developing PCD. Multivariable regression models were used to control for confounding variables such as age at diagnosis, gender, and disease location. The statistical analyses included descriptive statistics, propensity score matching, and inverse probability weighting to ensure robust results.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eResults\u003c/strong\u003e: A total of 187 cases were analyzed, with 41 cases of PCD and 146 cases of non-perianal CD. The presence of KIR2DS5 was significantly associated with an increased risk of PCD (OR = 2.49, 95% CI: 1.09–5.69, P = 0.031) after adjusting for multiple covariates. Subgroup analyses revealed potential interaction effects based on ancestral origins, with French-ancestry children in Montreal showing a higher susceptibility to PCD when the activating KIR2DS5 present.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eConclusion\u003c/strong\u003e: The study demonstrates that KIR2DS5 is a significant genetic risk factor for PCD in pediatric patients. This finding highlights the importance of genetic factors in the pathogenesis of PD and suggests that KIR2DS5 genotyping could serve as a potential biomarker for identifying high-risk pediatric patients with CD. Future research should focus on validating these findings in larger and more diverse populations and exploring targeted therapies based on genetic profiles.\u003c/p\u003e","manuscriptTitle":"Association between activating KIR and Perianal Crohn’s Disease in Pediatric Patients: A Nested case–control study","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2025-11-24 10:26:30","doi":"10.21203/rs.3.rs-7953845/v1","editorialEvents":[{"type":"communityComments","content":0},{"type":"decision","content":"Revision requested","date":"2026-05-08T12:13:41+00:00","index":"","fulltext":""},{"type":"editorInvitedReview","content":"","date":"2026-05-06T12:54:32+00:00","index":"hide","fulltext":""},{"type":"reviewerAgreed","content":"308890112587547758112003714006220975858","date":"2026-04-15T10:54:11+00:00","index":"hide","fulltext":""},{"type":"reviewerAgreed","content":"204329292712035719123636272916899912452","date":"2026-01-19T09:57:04+00:00","index":"hide","fulltext":""},{"type":"editorInvitedReview","content":"","date":"2025-12-08T15:38:58+00:00","index":"hide","fulltext":""},{"type":"reviewerAgreed","content":"164571642581703844915483332722821821116","date":"2025-11-17T18:54:22+00:00","index":"hide","fulltext":""},{"type":"reviewerAgreed","content":"1527203871425087538722359474665666929","date":"2025-11-14T14:06:03+00:00","index":"hide","fulltext":""},{"type":"reviewersInvited","content":"","date":"2025-11-12T16:47:11+00:00","index":"","fulltext":""},{"type":"editorInvited","content":"","date":"2025-10-31T20:28:08+00:00","index":"","fulltext":""},{"type":"editorAssigned","content":"","date":"2025-10-31T20:25:48+00:00","index":"","fulltext":""},{"type":"checksComplete","content":"","date":"2025-10-29T18:05:16+00:00","index":"","fulltext":""},{"type":"submitted","content":"Scientific Reports","date":"2025-10-29T18:02:06+00:00","index":"","fulltext":""}],"status":"published","journal":{"display":true,"email":"[email protected]","identity":"scientific-reports","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":false,"externalIdentity":"scirep","sideBox":"Learn more about [Scientific Reports](http://www.nature.com/srep/)","snPcode":"","submissionUrl":"","title":"Scientific Reports","twitterHandle":"","acdcEnabled":true,"dfaEnabled":true,"editorialSystem":"stoa","reportingPortfolio":"Scientific Reports","inReviewEnabled":true,"inReviewRevisionsEnabled":true}}],"origin":"","ownerIdentity":"d04e26fc-3f62-4a8a-aeb7-6091e39823b8","owner":[],"postedDate":"November 24th, 2025","published":true,"recentEditorialEvents":[{"type":"decision","content":"Revision requested","date":"2026-05-08T12:13:41+00:00","index":"","fulltext":""},{"type":"editorInvitedReview","content":"","date":"2026-05-06T12:54:32+00:00","index":136,"fulltext":""}],"rejectedJournal":[],"revision":"","amendment":"","status":"under-review","subjectAreas":[{"id":58493473,"name":"Health sciences/Diseases"},{"id":58493474,"name":"Health sciences/Gastroenterology"},{"id":58493475,"name":"Biological sciences/Genetics"},{"id":58493476,"name":"Biological sciences/Immunology"},{"id":58493477,"name":"Health sciences/Medical research"},{"id":58493478,"name":"Health sciences/Risk factors"}],"tags":[],"updatedAt":"2026-05-14T20:38:37+00:00","versionOfRecord":[],"versionCreatedAt":"2025-11-24 10:26:30","video":"","vorDoi":"","vorDoiUrl":"","workflowStages":[]},"version":"v1","identity":"rs-7953845","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-7953845","identity":"rs-7953845","version":["v1"]},"buildId":"8U1c8b4HqxoKbykW_rLl7","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}