Incidence of Chronic Recurrent Multifocal Osteomyelitis in Children and Adolescents in the UK and Republic of Ireland

Objectives Chronic Recurrent Multifocal Osteomyelitis (CRMO), also known as chronic nonbacterial osteomyelitis (CNO), is a rare autoinflammatory condition affecting the bones in children and teenagers. The actual incidence of CRMO remains uncertain. The objective of this study is to identify the incidence of CRMO in children and young people under the age of 16 years in the United Kingdom (UK) and Republic of Ireland (ROI). We also aim to delineate the demographics, clinical presentation, investigations, initial management and healthcare needs for children and adolescents with CRMO. Methods We conducted monthly surveys among all paediatric consultants and paediatric orthopaedic surgeons to identify patients newly diagnosed with CRMO between October 2020 and November 2022. A standardised questionnaire was sent to reporting clinicians to collect further information. Results Over the surveillance period, 288 patients were reported, among which, 165 confirmed and 20 probable cases were included in the analysis. The highest incidences were among 8-10 year-olds. A two-to-one female-to-male difference in incidence was observed, and male patients were more likely to present with multifocal disease. A negative correlation was observed between reporting clavicular and leg pain. Investigation-wise, 80.0% of patients were reported to have undergone whole-body MRI and 51.1% had bone biopsies. The most common initial treatments were NSAIDs (93.9%) and bisphosphonates (44.8%). Conclusion This study estimates an average annual CRMO incidence of 0.65 cases per 100,000 children and adolescents in the UK and ROI. These findings establish a crucial baseline for ongoing research and improvement in the care of individuals with CRMO. Key Messages The estimated annual incidence of CRMO is 0.65 per 100,000 children and adolescents aged <16. Two-fold higher incidence in females to males was found, with the highest incidence in 8-10 year-olds. Male patients are more likely to present with multifocal disease compared with females.