Plastic bronchitis complicated with mediastinal emphysema and subcutaneous emphysema due to bocavirus infection

Plastic bronchitis complicated with mediastinal emphysema and subcutaneous emphysema due to bocavirus infection | 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 Case Report Plastic bronchitis complicated with mediastinal emphysema and subcutaneous emphysema due to bocavirus infection na ling, Wei Tang, Ting-ting Lin, Ting-Yi Chen, Lan-Fang Tang This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-6496674/v1 This work is licensed under a CC BY 4.0 License Status: Posted Version 1 posted You are reading this latest preprint version Abstract Background: Bronchial cast disease often occurs as a complication following the Fontan procedure. In recent years, there have been an increasing number of reports in the literature on bronchial cast disease caused by pulmonary infections. However, the specific mechanisms underlying the development of bronchial cast disease are not yet fully understood. Case presentation: In this report, we present two cases of plastic bronchitis secondary to bocavirus infection. The patients were admitted to the hospital with fever, cough, and dyspnea as the main symptoms. Subsequent chest CT scans indicated pneumonia accompanied by bilateral neck and mediastinal emphysema, atelectasis, emphysema, and bronchial obstruction. The treatment primarily consisted of anti-infective therapy, symptomatic supportive care, bronchoalveolar lavage, and the removal of bronchial casts. After the extraction of bronchial casts and mucous plug-like secretions, both patients eventually entered a remission phase. Conclusion: Human bocavirus-associated plastic bronchitis should be considered in children with significant pulmonary lesions. Bronchoalveolar lavage may be performed promptly to alleviate disease progression. Plastic bronchitis Bocavirus Bronchoscopy Atelectasis Mediastinal emphysema Subcutaneous emphysema Figures Figure 1 Figure 2 Introduction Plastic bronchitis (PB) is a severe respiratory disease characterized by the formation of bronchial casts that obstruct the airways, leading to partial or complete impairment of pulmonary ventilation. Children with this condition often present with symptoms such as coughing, wheezing, shortness of breath, and fever. In severe cases, there may be manifestations of acute respiratory failure and even death [ 1 ] . The pathogenesis of PB is not well understood. The cast characteristics can be divided into 2 types. Type I casts (inflammatory casts) are composed primarily of eosinophils, neutrophils, and fibrin, and Charcot-Leyden crystals can also be observed. They are often secondary to pulmonary inflammatory diseases, asthma, and cystic fibrosis and are thought to be due to a weakened mucociliary clearance mechanism. Type II casts (mucinous casts) are acellular and are composed mainly of protein lymphatic substances, and this type is associated with congenital heart disease status after Fontan surgery [ 2 , 3 ] . PB currently lacks definitive diagnostic criteria, making early diagnosis difficult. The acute mortality rate in severe cases is high. According to the literature, the mortality rate for inflammatory cast PB is 6–50%, and for noninflammatory cast PB, it is 28–60% [ 2 , 4 ] . A prevalence of approximately 6.8/100,000 has been reported [ 5 ] . However, there are no definitive diagnostic criteria for PB, and many cases are likely undiagnosed or overshadowed by diagnoses of other diseases, suggesting that the prevalence rate may be underestimated [ 6 ] . Therefore, it is necessary for us to be vigilant. PB can be a complication of various diseases. In Western countries, the majority of pediatric cases of PB are associated with surgical correction of congenital heart disease [ 7 ] . In comparison, cases of PB secondary to infection and asthma are more frequently reported in the domestic literature [ 8 ] . The pathogens associated with PB are primarily Mycoplasma pneumoniae [ 9 ] , adenovirus [ 10 ] , and influenza virus [ 11 ] . It is rarely reported to be associated with human bocavirus (HBoV) [ 12 ] . Herein, we report the clinical features, diagnosis, and treatment of 2 healthy children who developed PB after HBoV infection. Case presentation Case 1 was a 3-year and 9-month-old girl with a cough for more than a month, worsening for 4 days, and fever for half a day. Initially, the cough was not severe and presented as paroxysmal bouts of coughing, mainly at night. The patient subsequently experienced an exacerbation of cough, with increased frequency and severity, turning red in the face during severe coughing episodes, accompanied by purulent nasal discharge. On physical examination, coarse breath sounds were noted in both lungs, with three depression sign and audible wheezing sounds. The child required 3 L/min nasal cannula oxygen to maintain normal oxygen saturation. Upon admission, routine blood tests revealed normal white blood cell counts with increased eosinophil counts. A chest X-ray upon admission revealed increased lung markings bilaterally (Figure 1A). Thus, the preliminary diagnoses are acute bronchitis, acute sinusitis and allergic rhinitis. Upon re-examination, routine blood tests revealed elevated inflammatory markers, and the child's IgE level was 831.0 IU/ml. The pediatric patient's respiratory pathogen nucleic acid 13-panel test was positive for rhinovirus and bocavirus. A neck and chest CT scan with airway reconstruction and a sinus CT scan revealed sinusitis, mediastinal emphysema, air accumulation in the bilateral neck, left submandibular region, and left anterior chest wall, pneumonia with segmental atelectasis of the left upper lobe, and signs of left-sided pneumothorax in the remaining lung, with the anterior segmental bronchus of the left upper lobe not being patent (Figure 1B-C). After admission, the child experienced recurrent fever and worsening cough, accompanied by wheezing, shortness of breath, and hoarseness. The child was treated with piperacillin-tazobactam sodium and methylprednisolone for anti-inflammatory therapy and intranasal fluticasone for sinusitis, along with ambroxol and triple nebulization for symptomatic treatment. After one week, the body temperature returned to normal, and the cough improved. A repeat chest radiograph revealed improvement in pneumonia compared with before, and air accumulation in the neck and upper chest soft tissues was no longer apparent. However, the child still experienced wheezing and shortness of breath, requiring nasal cannula oxygen to maintain normal oxygen saturation. Therefore, bronchoscopy was promptly performed on the child. Under bronchoscopy, mucus plugs were observed in the left main bronchus and the upper and lower left bronchi, which were removed multiple times with a foreign body basket, yielding several cast-like objects (Figure 2A-B). Suctioning and alveolar lavage were performed, and the lavage fluid was sent for bacterial smear, tuberculosis smear, sputum culture, and Mycoplasma pneumoniae DNA test, all of which were negative. After bronchoscopy, a subsequent chest radiograph revealed that pneumonia improved with absorption compared with before (Figure 1D). The child was ultimately diagnosed with acute severe bocavirus pneumonia, atelectasis, mediastinal emphysema, subcutaneous emphysema, pneumothorax, acute sinusitis, allergic rhinitis, and rhinovirus infection. After aggressive treatment, the child's general condition significantly improved, with no wheezing or shortness of breath. Oxygen was discontinued on the 10th day of hospitalization, and the child was discharged. Case 2 was a 3-year-3-month-old boy with a cough for 2 days, wheezing for one day, and fever for half a day. The child's illness was acute in onset, and on the second day of the illness, the child presented with labored breathing, wheezing, and shortness of breath, accompanied by fever with a peak temperature of 39.3°C. The child was brought to our emergency department for treatment. Under 4 L/min oxygen via a mask, the oxygen saturation fluctuated between 90% and 92%. The child was admitted to our pediatric intensive care unit (PICU). The physical examination revealed inspiratory retractions, fullness on the left side of the chest, a palpable crepitus of the subcutaneous tissues, an absence of breath sounds on the left lung, and coarse breath sounds on the right lung, with audible wheezing. The heart sounds are strong, the rhythm is regular, and no murmurs are heard in any valvular area. The abdomen was soft, without significant tenderness or rebound tenderness, and no hepatosplenomegaly was palpable. The neck is soft and free of resistance, and there are no significant positive neurological signs. The results of routine blood tests revealed a significant increase in the white blood cell count, predominantly that of neutrophils, with a high-sensitivity C-reactive protein level of 18.60 mg/L. Chest radiography revealed pneumothorax with underinflation of both upper lungs, mediastinal emphysema, bilateral lung inflammation, and extensive subcutaneous emphysema in the neck and left chest wall (Figure 1E). The respiratory pathogen nucleic acid 13-panel test was positive for rhinovirus and human bocavirus, indicating infection with rhinovirus and bocavirus. The IgE level was 409.0 IU/ml. The neck and chest CT scan with airway reconstruction revealed air accumulation in the right maxillofacial region, bilateral neck, thoracic back, and mediastinum, bilateral hydropneumothorax, atelectasis of the right upper and middle lobes and the left upper lobe, and obstruction of the bronchi in the right upper and middle lobes and the left upper lobe (Figure 1F-G). Therefore, the preliminary diagnosis is acute severe pneumonia, respiratory failure, hydropneumothorax, atelectasis, mediastinal emphysema, and subcutaneous emphysema. Upon admission, the child was critically ill and placed under intensive care with special attention to cardiopulmonary monitoring. Thoracentesis was performed on the child, from which 10 ml of gas was aspirated from the right side and 7 ml from the left side. In terms of treatment, the child received high-flow nasal cannula oxygen therapy at 6 L/min for 6 days, mask oxygen therapy for 2 days, and nasal catheter oxygen therapy for 2 days. Magnesium sulfate was administered intravenously for spasmolysis for 3 days, and cefoperazone-sulbactam was administered intravenously for anti-infection, along with methylprednisolone for anti-inflammatory treatment , for 9 days. During this period, ambroxol and nebulization were also provided for symptomatic supportive treatment. The child underwent bronchoscopy on the 4th and 8th days of hospitalization. During the child's first bronchoscopy, the bronchoscopic view revealed that most of the distal bronchial segments and branches were obstructed by mucus plugs(Figure 2C). The mucosa was congested and edematous. Treatment included lavage with normal saline, repeated suctioning, and the use of a foreign body basket to retrieve the mucus plugs repeatedly. A large amount of mucus plug-like material and mucoid liquid were removed (Figure 2D). After the first bronchoscopy, a follow-up chest radiograph revealed significant improvement in pneumothorax and underinflation of both upper lungs, as well as mediastinal gas accumulation, compared with previous findings. Compared with before, the subcutaneous emphysema in the neck and left chest wall had also been absorbed. During the child's second bronchoscopy, a small amount of white, viscous secretions were observed in the lumen of the left and right bronchi. After suctioning, the secretions decreased, and no mucus plug-like material was observed. After the second bronchoscopy, a chest radiograph revealed a marked improvement in pneumonia (Figure 1H), without significant cough or expectoration, wheezing, shortness of breath, or inspiratory retractions. Bilateral lung breath sounds were symmetrical without crackles or rhonchi heard. The child was ultimately diagnosed with acute severe bocavirus pneumonia, respiratory failure, plastic bronchitis, hydropneumothorax, pulmonary atelectasis, mediastinal emphysema, subcutaneous emphysema, and rhinovirus infection. Oxygen was discontinued on the 10th day of hospitalization, and the child's general condition improved significantly, leading to discharge. Discussion PB is a relatively rare respiratory disease that can be caused by a variety of conditions. In China, there are numerous reports in the literature regarding pulmonary infectious diseases as the primary cause of PB. The clinical manifestations of PB caused by infection mainly include fever and cough, with persistent high fever and a long duration of fever. Some patients exhibit wheezing and dyspnea, the severity of which is determined by the size and location of the pathogen and the bronchial molding model. The main physical signs are tachypnea, three depression sign, and decreased breath sounds on the affected side. The CT manifestations of PB are usually pulmonary consolidation, atelectasis, insufficient lung expansion, and compensatory emphysema. Therefore, when a child exhibits the above clinical characteristics, one should be aware of the possibility of developing PB. In this study, the average duration of fever in children was 4 days, and non-invasive ventilation was required to maintain oxygen saturation on the second day of hospitalization, indicating that pneumonia caused by bocavirus has a rapid onset and can cause severe complications within a short period. This article reports two cases associated with HBoV-related PB. Reports on PB caused by HBoV infection are very rare, making this case report of significant interest. The identification of HBoV in this case suggests that the virus may have a potential role in the formation of PB, indicating that the virus could trigger or exacerbate the formation of bronchial casts. HBoV is a small, non-enveloped, single-stranded DNA virus that primarily affects the lower respiratory tract and gastrointestinal tract in children [ 13 ] . In 2005, Tobias Allander first identified the virus in respiratory samples from 17 children with suspected viral-origin acute respiratory tract infections in Sweden [ 14 ] . HBoV has been identified in 4 genotypes, among which genotype 1 is most closely associated with respiratory tract infections [ 15 , 16 ] . Serological studies using recombinant HBoV1 capsid proteins as antigens have established causal relationships between HBoV1 and acute respiratory tract infection [ 17 ] . Since the initial identification of HBoV in nasopharyngeal secretions from children with lower respiratory tract infections in Sweden, its existence has reached a consensus both domestically and internationally. The respiratory and digestive system diseases caused by it have also gradually been studied and reported [ 18 , 19 ] . HBoV infection typically occurs in infants and children aged 6 to 24 months, but it can also be found in children over the age of 5 and in adults. HBoV infection can occur year-round, with varying epidemic seasons in different regions [ 20 ] . HBoV can cause respiratory symptoms ranging from mild to severe. Mild cases may present with non-specific symptoms such as fever, cough, nasal congestion, rhinorrhea, and wheezing or shortness of breath. Severe cases, in addition to the aforementioned non-specific manifestations, may also present complications such as pulmonary consolidation, atelectasis, and pleural effusion. HBoV infection can also exacerbate chronic pulmonary diseases such as asthma, chronic obstructive pulmonary disease (COPD), and cystic fibrosis [ 13 , 14 ] . Reports suggest that mixed infections are more likely to cause pneumonia [ 21 ] . A high co-detection rate is a recognized characteristic of HBoV infection, with the most common being human rhinovirus (HRV) (45%), human adenovirus (ADV) (30%), and respiratory syncytial virus (RSV) (7%) [ 22 ] . Reports indicate that RSV is the most common co-infection with HBoV in the Middle East and North Africa [ 23 ] . In the Chinese population reported by Tang et al., only 26.1% of children had mixed common respiratory viral infections, primarily human rhinovirus (HRV) (11.4%) and RSV (6%) [ 21 ] . These 2 cases are all mixed infections, where a respiratory pathogen panel detected a co-infection of HBov and HRV. The condition was severe, with symptoms beyond fever and cough, including atelectasis, mediastinal emphysema, subcutaneous emphysema, and pulmonary emphysema. The mechanism of HBoV-associated PB is unknown, and the link between HBoV and PB requires further research. Studies have indicated that HBoV can induce DNA damage in polarized airway epithelial cell cultures, leading to the destruction of epithelial barrier function. ASC-mediated NLRP3 appears to be the pattern recognition receptor that drives pyroptosis induced by HBoV infection. After HBoV activates the NLRP3 inflammasome, it induces the secretion of pro-inflammatory molecules and Th2 cytokines through caspase-1-mediated pyroptosis of epithelial cells. Additionally, HBoV infection promotes inflammation by increasing the expression of interleukin-1α (IL-1α) and IL-18. In this report, the bronchial casts were located on the left side, which is consistent with previous reports that PB is more likely to occur on the left side [ 24 ] . PB caused by infection is typically type I (inflammatory type), which is mainly formed by eosinophils, neutrophils, and fibrin. Children with allergic constitutions are more prone to develop PB [ 25 ] . The IgE levels of these two children were significantly elevated at 831.0 IU/ml and 409.0 IU/ml, indicating an allergic constitution, and these two children also had allergic rhinitis. Inflammatory casts are associated with eosinophilic inflammation, and studies have shown that HBoV is related to the acute exacerbation of asthma and has been reported in the literature to be involved in severe eosinophilic inflammation [ 26 ] . Studies have shown that stimulating CD4 + T cells with HBoV-specific antigens can induce the secretion of cytokines, including interferon-gamma (IFN-γ), interleukin-10 (IL-10), and interleukin-13 (IL-13). This finding suggests a link between HBoV infection and the exacerbation of asthma, indicating that HBoV may trigger or exacerbate the formation of bronchial casts [ 27 ] . However, the pathogenic mechanisms of HBoV infection are not yet fully understood and require further in-depth research. The potential link between HBoV infection and acute wheezing, bronchiolitis, and asthma may emerge as a new direction for research. At present, there is no specific treatment for PB caused by HBoV in clinical practice. Fiberoptic bronchoscopy plays a crucial role in the diagnosis and treatment of PB. It enables the visualization of bronchial casts. A diagnosis of PB can be made when bronchial casts are observed under the scope, and the removal of casts and secretions can significantly improve a child's pulmonary ventilation [ 28 ] . Other routine treatments that can be applied include antipyretics for fever reduction, bronchodilator nebulization, and intravenous administration of ambroxol for expectoration as symptomatic therapy [ 29 , 30 ] . If necessary, corticosteroids can be used, and if a child experiences hypoxia or wheezing with a decrease in oxygen saturation, non-invasive ventilation, such as oxygen administration via a nasal cannula or face mask, should be initiated [ 31 , 32 ] . In this report, both patients utilized non-invasive ventilation to maintain normal oxygen saturation, and fiberoptic bronchoscopy was performed immediately. Through bronchoscopy, many bronchial casts were removed from the left bronchus, and the impression from the bronchoscopy was PB. Following the removal of bronchial casts and mucous plug-like secretions via bronchoscopy, the children's condition were significantly improved. In conclusion, for children presenting with fever, cough, wheezing, retractions and difficulty breathing, considering PB is essential. Early recognition and timely, aggressive treatment can significantly improve patient prognosis. We report here two cases of PB caused by co-infection with HBoV and rhinovirus, and by employing fiberoptic bronchoscopy to address bronchial obstruction, we highlight the importance of considering PB in seriously ill children with HBoV infection as early as possible and demonstrate the benefits of using fiberoptic bronchoscopy in the diagnosis and treatment of such diseases. Declarations Ethics approval and consent to participate This study was conducted in accordance with the Declaration of Helsinki and was approved by the Ethics Committee of Children’s Hospital of Zhejiang University School of Medicine. Written informed consent to participate in this study was provided by the patient and his parents. Informed consent The patient and his parents gave informed consent to the use of the images and information for research in an online openaccess publication. Competing interests The authors declare no competing interests. Funding This study was supported by the National Natural Science Foundation of China (82070028), the Innovation Team for the Diagnosis and Treatment of Childhood Asthma (2022), and the Key R & D Projects of Zhejiang Provincial Science and Technology Agency (2023C03042). Author Contribution Na wrote the main manuscript text ,Tang Wei and Lin Ting-Ting prepared figures 1. Chen Ting-Yi prepared figure 2. All authors reviewed the manuscript Data availability Data is provided within the manuscript or supplementary information fles. References Park J, Elshami A, Kang D, Jung T. Plastic bronchitis. Eur Respir J 1996; 9: 612–614. 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Prevalence and Clinical Characterization of Bocavirus Infection in a Specialized Children’s Hospital in Saudi Arabia. Cureus 2022; 14: e22127. [PMID: 35308707 DOI: 10.7759/cureus.22127] M P, J V, C A, J S, A G-S, A C-C, N S, J E, A R, Mj I-C, J Q, A S-A, P S-P, T P, A A. Molecular characterization and clinical impact of human bocavirus at a tertiary hospital in Barcelona (Catalonia, Spain) during the 2014-2017 seasons. Infection 2023; 51. [PMID: 36401674 DOI: 10.1007/s15010-022-01955-z] D AT, E Y, N E, B O, A A, B S, O G, D D, U O, N K. Human bocavirus and human metapneumovirus in children with lower respiratory tract infections: Effects on clinical, microbiological features and disease severity. Pediatr Int Off J Jpn Pediatr Soc 2022; 64. [PMID: 35616205 DOI: 10.1111/ped.15102] Additional Declarations No competing interests reported. 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Also discoverable on Platform About Our Team In Review Editorial Policies Advisory Board Help Center Resources Author Services Accessibility API Access RSS feed Manage Cookie Preferences © Research Square 2026 | ISSN 2693-5015 (online) Privacy Policy Terms of Service Do Not Sell My Personal Information {"props":{"pageProps":{"initialData":{"identity":"rs-6496674","acceptedTermsAndConditions":true,"allowDirectSubmit":true,"archivedVersions":[],"articleType":"Case Report","associatedPublications":[],"authors":[{"id":475959082,"identity":"b0ef5df3-3750-47f5-b2c7-c334f9f8357d","order_by":0,"name":"na ling","email":"","orcid":"","institution":"Children’s Hospital of Zhejiang University School of Medicine","correspondingAuthor":false,"prefix":"","firstName":"na","middleName":"","lastName":"ling","suffix":""},{"id":475959084,"identity":"ad6ea2d9-a085-43a0-8250-f2d5f0f02c54","order_by":1,"name":"Wei Tang","email":"","orcid":"","institution":"Children’s Hospital of Zhejiang University School of Medicine","correspondingAuthor":false,"prefix":"","firstName":"Wei","middleName":"","lastName":"Tang","suffix":""},{"id":475959086,"identity":"4906d268-2a66-4c3e-9aee-2d6ca7e3208a","order_by":2,"name":"Ting-ting Lin","email":"","orcid":"","institution":"Children’s Hospital of Zhejiang University School of Medicine","correspondingAuthor":false,"prefix":"","firstName":"Ting-ting","middleName":"","lastName":"Lin","suffix":""},{"id":475959089,"identity":"0cebd0c4-8f8a-4ef6-9507-5fd0983d3cd6","order_by":3,"name":"Ting-Yi Chen","email":"","orcid":"","institution":"Children’s Hospital of Zhejiang University School of Medicine","correspondingAuthor":false,"prefix":"","firstName":"Ting-Yi","middleName":"","lastName":"Chen","suffix":""},{"id":475959090,"identity":"ae95ed6a-2e3b-4374-929a-4c72b7310c95","order_by":4,"name":"Lan-Fang Tang","email":"data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAZAAAAAyAQMAAABI0h/eAAAABlBMVEX///8AAABVwtN+AAAACXBIWXMAAA7EAAAOxAGVKw4bAAAA4klEQVRIiWNgGAWjYBACfmbm4x8SDP7LMTAcAHLZiNAi2c6WxvChgtmYeC0G/TxmjDPOMCc2gLlEaWHmMXvM28aWPr/xjAHDh7LDDPyzG/BrMWdmKzfmbePJbWw4Y8A449xhBok7B/BrsWxm3iDN2yaR28xwxoCZt+0wg4FEAgGHAdUAtRiks4G0/CVOC4uZ5IwzCQk8IC2MxGiRbGZLNvhQccBwBsOxgoM959J5JG4Q0MLPf/jggwSDA/LyMw5vfPCjzFqOfwYBLQggcQAcmTzEqgfZ10CC4lEwCkbBKBhRAABqC0KzlkGkRAAAAABJRU5ErkJggg==","orcid":"","institution":"Children’s Hospital of Zhejiang University School of Medicine","correspondingAuthor":true,"prefix":"","firstName":"Lan-Fang","middleName":"","lastName":"Tang","suffix":""}],"badges":[],"createdAt":"2025-04-21 13:53:24","currentVersionCode":1,"declarations":"","doi":"10.21203/rs.3.rs-6496674/v1","doiUrl":"https://doi.org/10.21203/rs.3.rs-6496674/v1","draftVersion":[],"editorialEvents":[],"editorialNote":"","failedWorkflow":false,"files":[{"id":85648070,"identity":"554ca1fb-ad21-46b3-9faf-f912a128fdbe","added_by":"auto","created_at":"2025-06-30 08:52:46","extension":"png","order_by":1,"title":"Figure 1","display":"","copyAsset":false,"role":"figure","size":407847,"visible":true,"origin":"","legend":"\u003cp\u003eImaging of the patient. (A) A chest image of case 1 before bronchoscopy revealedincreased lung markings bilaterally. (B-C) A neck and chest CT scan revealed pneumoniawith segmental atelectasis of the left upper lobe, signs of left-sided emphysema, obstruction of the anterior segmental bronchus of the left upper lobe, mediastinal emphysema, and subcutaneous emphysema in the bilateral neck, left submandibular region, left axilla, and anterior chest wall. (D) A chest image of case 1 after bronchoscopy revealedimproved absorption compared with before. (E) A chest image of case 2 before bronchoscopy revealed pneumothorax with underinflation of both upper lungs, mediastinal emphysema, bilateral lung inflammation, and extensive subcutaneous emphysema in the neck and left chest wall. (F-G) A neck and chest CT scan revealed air accumulation in the right maxillofacial region, bilateral neck, thoracic back, and mediastinum, bilateral hydropneumothorax, atelectasis of the right upper and middle lobes and the left upper lobe, and obstruction of the bronchi in the right upper and middle lobes and the left upper lobe. (H) A chest image of case 2 after bronchoscopy revealedmarked improvement in pneumonia.\u003c/p\u003e","description":"","filename":"1.png","url":"https://assets-eu.researchsquare.com/files/rs-6496674/v1/5e27eca0300239fd023eaf9b.png"},{"id":85648071,"identity":"c336d7f1-21fc-4c26-8030-8144b7cb8181","added_by":"auto","created_at":"2025-06-30 08:52:46","extension":"png","order_by":2,"title":"Figure 2","display":"","copyAsset":false,"role":"figure","size":346075,"visible":true,"origin":"","legend":"\u003cp\u003eFindings during bronchoscopy. (A) Completeobstruction of the bronchus by a white elastic substance was observed in case 1. (B) Bronchial dendritic casts were successfully extracted.\u003c/p\u003e\n\u003cp\u003e(C) Imaging changes after using fiberoptic bronchoscopy. (D) Complete obstruction of the bronchus by a white elastic substance was observed in case 2. (E) Bronchial dendritic casts were successfully extracted.(F) Imaging changes after using fiberoptic bronchoscopy.\u003c/p\u003e","description":"","filename":"2.png","url":"https://assets-eu.researchsquare.com/files/rs-6496674/v1/f2bb99d43e53ee2e3426d450.png"},{"id":100955890,"identity":"5881445e-46fa-460c-a874-05daefde6e43","added_by":"auto","created_at":"2026-01-23 07:29:24","extension":"pdf","order_by":0,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":1398517,"visible":true,"origin":"","legend":"","description":"","filename":"manuscript.pdf","url":"https://assets-eu.researchsquare.com/files/rs-6496674/v1/1adc4fe5-13e5-4cdb-a967-96f77936c6eb.pdf"}],"financialInterests":"No competing interests reported.","formattedTitle":"Plastic bronchitis complicated with mediastinal emphysema and subcutaneous emphysema due to bocavirus infection","fulltext":[{"header":"Introduction","content":"\u003cp\u003ePlastic bronchitis (PB) is a severe respiratory disease characterized by the formation of bronchial casts that obstruct the airways, leading to partial or complete impairment of pulmonary ventilation. Children with this condition often present with symptoms such as coughing, wheezing, shortness of breath, and fever. In severe cases, there may be manifestations of acute respiratory failure and even death \u003csup\u003e[\u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e1\u003c/span\u003e]\u003c/sup\u003e. The pathogenesis of PB is not well understood. The cast characteristics can be divided into 2 types. Type I casts (inflammatory casts) are composed primarily of eosinophils, neutrophils, and fibrin, and Charcot-Leyden crystals can also be observed. They are often secondary to pulmonary inflammatory diseases, asthma, and cystic fibrosis and are thought to be due to a weakened mucociliary clearance mechanism. Type II casts (mucinous casts) are acellular and are composed mainly of protein lymphatic substances, and this type is associated with congenital heart disease status after Fontan surgery \u003csup\u003e[\u003cspan citationid=\"CR2\" class=\"CitationRef\"\u003e2\u003c/span\u003e, \u003cspan citationid=\"CR3\" class=\"CitationRef\"\u003e3\u003c/span\u003e]\u003c/sup\u003e. PB currently lacks definitive diagnostic criteria, making early diagnosis difficult. The acute mortality rate in severe cases is high. According to the literature, the mortality rate for inflammatory cast PB is 6\u0026ndash;50%, and for noninflammatory cast PB, it is 28\u0026ndash;60% \u003csup\u003e[\u003cspan citationid=\"CR2\" class=\"CitationRef\"\u003e2\u003c/span\u003e, \u003cspan citationid=\"CR4\" class=\"CitationRef\"\u003e4\u003c/span\u003e]\u003c/sup\u003e.\u003c/p\u003e \u003cp\u003eA prevalence of approximately 6.8/100,000 has been reported\u003csup\u003e[\u003cspan citationid=\"CR5\" class=\"CitationRef\"\u003e5\u003c/span\u003e]\u003c/sup\u003e. However, there are no definitive diagnostic criteria for PB, and many cases are likely undiagnosed or overshadowed by diagnoses of other diseases, suggesting that the prevalence rate may be underestimated \u003csup\u003e[\u003cspan citationid=\"CR6\" class=\"CitationRef\"\u003e6\u003c/span\u003e]\u003c/sup\u003e. Therefore, it is necessary for us to be vigilant. PB can be a complication of various diseases. In Western countries, the majority of pediatric cases of PB are associated with surgical correction of congenital heart disease \u003csup\u003e[\u003cspan citationid=\"CR7\" class=\"CitationRef\"\u003e7\u003c/span\u003e]\u003c/sup\u003e. In comparison, cases of PB secondary to infection and asthma are more frequently reported in the domestic literature \u003csup\u003e[\u003cspan citationid=\"CR8\" class=\"CitationRef\"\u003e8\u003c/span\u003e]\u003c/sup\u003e. The pathogens associated with PB are primarily \u003cem\u003eMycoplasma pneumoniae\u003c/em\u003e \u003csup\u003e[\u003cspan citationid=\"CR9\" class=\"CitationRef\"\u003e9\u003c/span\u003e]\u003c/sup\u003e, adenovirus \u003csup\u003e[\u003cspan citationid=\"CR10\" class=\"CitationRef\"\u003e10\u003c/span\u003e]\u003c/sup\u003e, and influenza virus \u003csup\u003e[\u003cspan citationid=\"CR11\" class=\"CitationRef\"\u003e11\u003c/span\u003e]\u003c/sup\u003e. It is rarely reported to be associated with human bocavirus (HBoV) \u003csup\u003e[\u003cspan citationid=\"CR12\" class=\"CitationRef\"\u003e12\u003c/span\u003e]\u003c/sup\u003e. Herein, we report the clinical features, diagnosis, and treatment of 2 healthy children who developed PB after HBoV infection.\u003c/p\u003e"},{"header":"Case presentation","content":"\u003cp\u003eCase 1 was a 3-year and 9-month-old girl with a cough for more than a month, worsening for 4 days, and fever for half a day. Initially, the cough was not severe and presented as paroxysmal bouts of coughing, mainly at night. The patient subsequently experienced an exacerbation of cough, with increased frequency and severity, turning red in the face during severe coughing episodes, accompanied by purulent nasal discharge.\u003c/p\u003e\n\u003cp\u003eOn physical examination, coarse breath sounds were noted in both lungs, with three depression sign and audible wheezing sounds. The child required 3 L/min nasal cannula oxygen to maintain normal oxygen saturation.\u003c/p\u003e\n\u003cp\u003eUpon admission, routine blood tests revealed normal white blood cell counts with increased eosinophil counts. A chest X-ray upon admission revealed increased lung markings bilaterally\u0026nbsp;(Figure 1A). Thus, the preliminary diagnoses are acute bronchitis, acute sinusitis and allergic rhinitis.\u003c/p\u003e\n\u003cp\u003eUpon re-examination, routine blood tests revealed elevated inflammatory markers, and the child's IgE level was 831.0 IU/ml.\u0026nbsp;The pediatric patient's respiratory pathogen nucleic acid 13-panel test\u0026nbsp;was\u0026nbsp;positive for rhinovirus and bocavirus. A neck and chest CT scan with airway reconstruction and a sinus CT scan revealed sinusitis, mediastinal emphysema, air accumulation in the bilateral neck, left submandibular region, and left anterior chest wall, pneumonia with segmental atelectasis of the left upper lobe, and signs of left-sided pneumothorax in the remaining lung, with the anterior segmental bronchus of the left upper lobe not being patent (Figure 1B-C).\u0026nbsp;After admission, the child experienced recurrent fever\u0026nbsp;and\u0026nbsp;worsening cough, accompanied by wheezing,\u0026nbsp;shortness of breath, and hoarseness. The child was treated with piperacillin-tazobactam sodium and methylprednisolone for anti-inflammatory therapy and intranasal fluticasone for sinusitis, along with ambroxol and triple nebulization for symptomatic treatment. After one week, the body temperature returned to normal, and the cough improved. A repeat chest radiograph\u0026nbsp;revealed\u0026nbsp;improvement in pneumonia compared\u0026nbsp;with\u0026nbsp;before, and air accumulation in the neck and upper chest soft tissues was no longer apparent. However, the child still experienced wheezing and shortness of breath, requiring nasal cannula oxygen to maintain normal oxygen saturation. Therefore, bronchoscopy was promptly performed on the child.\u003c/p\u003e\n\u003cp\u003eUnder bronchoscopy, mucus plugs were observed in the left main bronchus and the upper and lower left bronchi, which were removed multiple times with a foreign body basket, yielding several cast-like objects (Figure 2A-B). Suctioning and alveolar lavage were performed, and the lavage fluid was sent for bacterial smear, tuberculosis smear, sputum culture, and \u003cem\u003eMycoplasma pneumoniae\u003c/em\u003e DNA test, all of which were negative.\u0026nbsp;After bronchoscopy, a subsequent chest radiograph revealed that pneumonia improved with absorption compared with before (Figure 1D). The child was ultimately diagnosed with acute severe bocavirus pneumonia, atelectasis, mediastinal emphysema, subcutaneous emphysema, pneumothorax, acute sinusitis, allergic rhinitis, and rhinovirus infection. After aggressive treatment, the child's general condition significantly improved, with no wheezing or shortness of breath. Oxygen was discontinued on the 10th day of hospitalization, and the child was discharged.\u003c/p\u003e\n\u003cp\u003eCase 2 was a 3-year-3-month-old boy with a cough for 2 days, wheezing for one day, and fever for half a day.\u0026nbsp;The child's illness was acute in onset, and on the second day of the illness, the child presented with labored breathing, wheezing, and shortness of breath, accompanied by fever with a peak temperature of 39.3°C. The child was brought to our emergency department for treatment. Under 4 L/min oxygen via a mask, the oxygen saturation fluctuated between 90% and 92%. The child was admitted to our pediatric intensive care unit (PICU).\u003c/p\u003e\n\u003cp\u003eThe physical examination revealed inspiratory retractions, fullness on the left side of the chest, a palpable crepitus of the subcutaneous tissues, an absence of breath sounds on the left lung, and coarse breath sounds on the right lung, with audible wheezing.\u0026nbsp;The heart sounds are strong, the rhythm is regular, and no murmurs are heard in\u0026nbsp;any\u0026nbsp;valvular\u0026nbsp;area.\u0026nbsp;The abdomen\u0026nbsp;was\u0026nbsp;soft, without significant tenderness or rebound tenderness, and no hepatosplenomegaly\u0026nbsp;was\u0026nbsp;palpable. The neck is soft\u0026nbsp;and free of\u0026nbsp;resistance, and there are no significant positive neurological signs.\u003c/p\u003e\n\u003cp\u003eThe results of routine blood tests revealed a significant increase in the white blood cell count, predominantly that of neutrophils, with a high-sensitivity C-reactive protein level of 18.60 mg/L. Chest radiography revealed pneumothorax with underinflation of both upper lungs, mediastinal emphysema, bilateral lung inflammation, and extensive subcutaneous emphysema in the neck and left chest wall (Figure 1E).\u0026nbsp;The respiratory pathogen nucleic acid 13-panel test\u0026nbsp;was\u0026nbsp;positive for rhinovirus and\u0026nbsp;human bocavirus, indicating\u0026nbsp;infection\u0026nbsp;with rhinovirus and bocavirus. The IgE level was 409.0 IU/ml. The neck and chest CT scan with airway reconstruction revealed air accumulation in the right maxillofacial region, bilateral neck, thoracic back, and mediastinum, bilateral hydropneumothorax, atelectasis of the right upper and middle lobes and the left upper lobe, and obstruction of the bronchi in the right upper and middle lobes and the left upper lobe (Figure 1F-G).\u0026nbsp;Therefore, the preliminary diagnosis is acute severe pneumonia, respiratory failure, hydropneumothorax, atelectasis, mediastinal emphysema,\u0026nbsp;and\u0026nbsp;subcutaneous emphysema.\u0026nbsp;\u003c/p\u003e\n\u003cp\u003eUpon admission, the child was critically ill and placed under intensive care with special attention to cardiopulmonary monitoring. Thoracentesis was performed on the child, from which 10 ml of gas was aspirated from the right side and 7 ml from the left side.\u0026nbsp;In terms of treatment, the child received high-flow nasal cannula oxygen therapy at 6 L/min for 6 days, mask oxygen therapy for 2 days, and nasal catheter oxygen therapy for 2 days. Magnesium sulfate was administered intravenously for spasmolysis for 3 days, and cefoperazone-sulbactam was administered intravenously for anti-infection, along with methylprednisolone for anti-inflammatory treatment\u003cins cite=\"mailto:Rubriq\" datetime=\"2025-03-31T00:48\"\u003e,\u003c/ins\u003e for 9 days. During this period, ambroxol and nebulization were also provided for symptomatic supportive treatment.\u003c/p\u003e\n\u003cp\u003eThe child underwent bronchoscopy on the 4th and 8th days of hospitalization. During the child's first bronchoscopy, the bronchoscopic view revealed that most of the distal bronchial segments and branches were obstructed by mucus plugs(Figure 2C). The mucosa was congested and edematous. Treatment included lavage with normal saline, repeated suctioning, and the use of a foreign body basket to retrieve the mucus plugs repeatedly. A large amount of mucus plug-like material and mucoid liquid were removed (Figure 2D). After the first bronchoscopy, a follow-up chest radiograph revealed significant improvement in pneumothorax and underinflation of both upper lungs, as well as mediastinal gas accumulation, compared with previous findings. Compared with before, the subcutaneous emphysema in the neck and left chest wall had also been absorbed. During the child's second bronchoscopy, a small amount of white, viscous secretions were observed in the lumen of the left and right bronchi. After suctioning, the secretions decreased, and no mucus plug-like material was observed. After the second bronchoscopy, a chest radiograph revealed a marked improvement in pneumonia (Figure 1H), without significant cough or expectoration, wheezing, shortness of breath, or inspiratory retractions. Bilateral lung breath sounds were symmetrical without crackles or rhonchi heard. The child was ultimately diagnosed with acute severe bocavirus pneumonia, respiratory failure, plastic bronchitis, hydropneumothorax, pulmonary atelectasis, mediastinal emphysema, subcutaneous emphysema, and rhinovirus infection. Oxygen was discontinued on the 10th day of hospitalization, and the child's general condition improved significantly, leading to discharge.\u003c/p\u003e"},{"header":"Discussion","content":"\u003cp\u003ePB is a relatively rare respiratory disease that can be caused by a variety of conditions. In China, there are numerous reports in the literature regarding pulmonary infectious diseases as the primary cause of PB. The clinical manifestations of PB caused by infection mainly include fever and cough, with persistent high fever and a long duration of fever. Some patients exhibit wheezing and dyspnea, the severity of which is determined by the size and location of the pathogen and the bronchial molding model. The main physical signs are tachypnea, three depression sign, and decreased breath sounds on the affected side. The CT manifestations of PB are usually pulmonary consolidation, atelectasis, insufficient lung expansion, and compensatory emphysema. Therefore, when a child exhibits the above clinical characteristics, one should be aware of the possibility of developing PB. In this study, the average duration of fever in children was 4 days, and non-invasive ventilation was required to maintain oxygen saturation on the second day of hospitalization, indicating that pneumonia caused by bocavirus has a rapid onset and can cause severe complications within a short period. This article reports two cases associated with HBoV-related PB. Reports on PB caused by HBoV infection are very rare, making this case report of significant interest. The identification of HBoV in this case suggests that the virus may have a potential role in the formation of PB, indicating that the virus could trigger or exacerbate the formation of bronchial casts.\u003c/p\u003e \u003cp\u003eHBoV is a small, non-enveloped, single-stranded DNA virus that primarily affects the lower respiratory tract and gastrointestinal tract in children \u003csup\u003e[\u003cspan citationid=\"CR13\" class=\"CitationRef\"\u003e13\u003c/span\u003e]\u003c/sup\u003e. In 2005, Tobias Allander first identified the virus in respiratory samples from 17 children with suspected viral-origin acute respiratory tract infections in Sweden \u003csup\u003e[\u003cspan citationid=\"CR14\" class=\"CitationRef\"\u003e14\u003c/span\u003e]\u003c/sup\u003e. HBoV has been identified in 4 genotypes, among which genotype 1 is most closely associated with respiratory tract infections \u003csup\u003e[\u003cspan citationid=\"CR15\" class=\"CitationRef\"\u003e15\u003c/span\u003e, \u003cspan citationid=\"CR16\" class=\"CitationRef\"\u003e16\u003c/span\u003e]\u003c/sup\u003e. Serological studies using recombinant HBoV1 capsid proteins as antigens have established causal relationships between HBoV1 and acute respiratory tract infection \u003csup\u003e[\u003cspan citationid=\"CR17\" class=\"CitationRef\"\u003e17\u003c/span\u003e]\u003c/sup\u003e.\u003c/p\u003e \u003cp\u003eSince the initial identification of HBoV in nasopharyngeal secretions from children with lower respiratory tract infections in Sweden, its existence has reached a consensus both domestically and internationally. The respiratory and digestive system diseases caused by it have also gradually been studied and reported \u003csup\u003e[\u003cspan citationid=\"CR18\" class=\"CitationRef\"\u003e18\u003c/span\u003e, \u003cspan citationid=\"CR19\" class=\"CitationRef\"\u003e19\u003c/span\u003e]\u003c/sup\u003e. HBoV infection typically occurs in infants and children aged 6 to 24 months, but it can also be found in children over the age of 5 and in adults. HBoV infection can occur year-round, with varying epidemic seasons in different regions \u003csup\u003e[\u003cspan citationid=\"CR20\" class=\"CitationRef\"\u003e20\u003c/span\u003e]\u003c/sup\u003e. HBoV can cause respiratory symptoms ranging from mild to severe. Mild cases may present with non-specific symptoms such as fever, cough, nasal congestion, rhinorrhea, and wheezing or shortness of breath. Severe cases, in addition to the aforementioned non-specific manifestations, may also present complications such as pulmonary consolidation, atelectasis, and pleural effusion. HBoV infection can also exacerbate chronic pulmonary diseases such as asthma, chronic obstructive pulmonary disease (COPD), and cystic fibrosis \u003csup\u003e[\u003cspan citationid=\"CR13\" class=\"CitationRef\"\u003e13\u003c/span\u003e, \u003cspan citationid=\"CR14\" class=\"CitationRef\"\u003e14\u003c/span\u003e]\u003c/sup\u003e. Reports suggest that mixed infections are more likely to cause pneumonia\u003csup\u003e[\u003cspan citationid=\"CR21\" class=\"CitationRef\"\u003e21\u003c/span\u003e]\u003c/sup\u003e. A high co-detection rate is a recognized characteristic of HBoV infection, with the most common being human rhinovirus (HRV) (45%), human adenovirus (ADV) (30%), and respiratory syncytial virus (RSV) (7%)\u003csup\u003e[\u003cspan citationid=\"CR22\" class=\"CitationRef\"\u003e22\u003c/span\u003e]\u003c/sup\u003e. Reports indicate that RSV is the most common co-infection with HBoV in the Middle East and North Africa \u003csup\u003e[\u003cspan citationid=\"CR23\" class=\"CitationRef\"\u003e23\u003c/span\u003e]\u003c/sup\u003e. In the Chinese population reported by Tang et al., only 26.1% of children had mixed common respiratory viral infections, primarily human rhinovirus (HRV) (11.4%) and RSV (6%)\u003csup\u003e[\u003cspan citationid=\"CR21\" class=\"CitationRef\"\u003e21\u003c/span\u003e]\u003c/sup\u003e. These 2 cases are all mixed infections, where a respiratory pathogen panel detected a co-infection of HBov and HRV. The condition was severe, with symptoms beyond fever and cough, including atelectasis, mediastinal emphysema, subcutaneous emphysema, and pulmonary emphysema.\u003c/p\u003e \u003cp\u003eThe mechanism of HBoV-associated PB is unknown, and the link between HBoV and PB requires further research. Studies have indicated that HBoV can induce DNA damage in polarized airway epithelial cell cultures, leading to the destruction of epithelial barrier function. ASC-mediated NLRP3 appears to be the pattern recognition receptor that drives pyroptosis induced by HBoV infection. After HBoV activates the NLRP3 inflammasome, it induces the secretion of pro-inflammatory molecules and Th2 cytokines through caspase-1-mediated pyroptosis of epithelial cells. Additionally, HBoV infection promotes inflammation by increasing the expression of interleukin-1α (IL-1α) and IL-18.\u003c/p\u003e \u003cp\u003eIn this report, the bronchial casts were located on the left side, which is consistent with previous reports that PB is more likely to occur on the left side \u003csup\u003e[\u003cspan citationid=\"CR24\" class=\"CitationRef\"\u003e24\u003c/span\u003e]\u003c/sup\u003e. PB caused by infection is typically type I (inflammatory type), which is mainly formed by eosinophils, neutrophils, and fibrin. Children with allergic constitutions are more prone to develop PB \u003csup\u003e[\u003cspan citationid=\"CR25\" class=\"CitationRef\"\u003e25\u003c/span\u003e]\u003c/sup\u003e. The IgE levels of these two children were significantly elevated at 831.0 IU/ml and 409.0 IU/ml, indicating an allergic constitution, and these two children also had allergic rhinitis. Inflammatory casts are associated with eosinophilic inflammation, and studies have shown that HBoV is related to the acute exacerbation of asthma and has been reported in the literature to be involved in severe eosinophilic inflammation \u003csup\u003e[\u003cspan citationid=\"CR26\" class=\"CitationRef\"\u003e26\u003c/span\u003e]\u003c/sup\u003e. Studies have shown that stimulating CD4\u003csup\u003e+\u003c/sup\u003e T cells with HBoV-specific antigens can induce the secretion of cytokines, including interferon-gamma (IFN-γ), interleukin-10 (IL-10), and interleukin-13 (IL-13). This finding suggests a link between HBoV infection and the exacerbation of asthma, indicating that HBoV may trigger or exacerbate the formation of bronchial casts \u003csup\u003e[\u003cspan citationid=\"CR27\" class=\"CitationRef\"\u003e27\u003c/span\u003e]\u003c/sup\u003e. However, the pathogenic mechanisms of HBoV infection are not yet fully understood and require further in-depth research. The potential link between HBoV infection and acute wheezing, bronchiolitis, and asthma may emerge as a new direction for research.\u003c/p\u003e \u003cp\u003eAt present, there is no specific treatment for PB caused by HBoV in clinical practice. Fiberoptic bronchoscopy plays a crucial role in the diagnosis and treatment of PB. It enables the visualization of bronchial casts. A diagnosis of PB can be made when bronchial casts are observed under the scope, and the removal of casts and secretions can significantly improve a child's pulmonary ventilation\u003csup\u003e[\u003cspan citationid=\"CR28\" class=\"CitationRef\"\u003e28\u003c/span\u003e]\u003c/sup\u003e. Other routine treatments that can be applied include antipyretics for fever reduction, bronchodilator nebulization, and intravenous administration of ambroxol for expectoration as symptomatic therapy\u003csup\u003e[\u003cspan citationid=\"CR29\" class=\"CitationRef\"\u003e29\u003c/span\u003e, \u003cspan citationid=\"CR30\" class=\"CitationRef\"\u003e30\u003c/span\u003e]\u003c/sup\u003e. If necessary, corticosteroids can be used, and if a child experiences hypoxia or wheezing with a decrease in oxygen saturation, non-invasive ventilation, such as oxygen administration via a nasal cannula or face mask, should be initiated\u003csup\u003e[\u003cspan citationid=\"CR31\" class=\"CitationRef\"\u003e31\u003c/span\u003e, \u003cspan citationid=\"CR32\" class=\"CitationRef\"\u003e32\u003c/span\u003e]\u003c/sup\u003e. In this report, both patients utilized non-invasive ventilation to maintain normal oxygen saturation, and fiberoptic bronchoscopy was performed immediately. Through bronchoscopy, many bronchial casts were removed from the left bronchus, and the impression from the bronchoscopy was PB. Following the removal of bronchial casts and mucous plug-like secretions via bronchoscopy, the children's condition were significantly improved.\u003c/p\u003e \u003cp\u003eIn conclusion, for children presenting with fever, cough, wheezing, retractions and difficulty breathing, considering PB is essential. Early recognition and timely, aggressive treatment can significantly improve patient prognosis. We report here two cases of PB caused by co-infection with HBoV and rhinovirus, and by employing fiberoptic bronchoscopy to address bronchial obstruction, we highlight the importance of considering PB in seriously ill children with HBoV infection as early as possible and demonstrate the benefits of using fiberoptic bronchoscopy in the diagnosis and treatment of such diseases.\u003c/p\u003e"},{"header":"Declarations","content":"\u003cp\u003e\u003cstrong\u003eEthics approval and consent to participate\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThis study was conducted in accordance with the Declaration of Helsinki and was approved by the Ethics Committee of Children\u0026rsquo;s Hospital of Zhejiang University School of Medicine. Written informed consent to participate in this study was provided by the patient and his parents.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eInformed consent\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe patient and his parents gave informed consent to the use of the images and information for research in an online openaccess publication.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eCompeting interests\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe authors declare no competing interests.\u003c/p\u003e\n\u003ch2\u003eFunding\u003c/h2\u003e\n\u003cp\u003eThis study was supported by the National Natural Science Foundation of China (82070028), the Innovation Team for the Diagnosis and Treatment of Childhood Asthma (2022), and the Key R \u0026amp; D Projects of Zhejiang Provincial Science and Technology Agency (2023C03042).\u003c/p\u003e\n\u003ch2\u003eAuthor Contribution\u003c/h2\u003e\n\u003cp\u003eNa wrote the main manuscript text ,Tang Wei and Lin Ting-Ting prepared figures 1. Chen Ting-Yi prepared figure 2. All authors reviewed the manuscript\u003c/p\u003e\n\u003ch2\u003eData availability\u003c/h2\u003e\n\u003cp\u003eData is provided within the manuscript or supplementary information fles.\u003c/p\u003e"},{"header":"References","content":"\u003col\u003e\n\u003cli\u003ePark J, Elshami A, Kang D, Jung T. Plastic bronchitis. \u003cem\u003eEur Respir J\u003c/em\u003e 1996; 9: 612–614. [DOI: 10.1183/09031936.96.09030612]\u003c/li\u003e\n\u003cli\u003eSeear M, Hui H, Magee F, Bohn D, Cutz E. Bronchial casts in children: a proposed classification based on nine cases and a review of the literature. \u003cem\u003eAm J Respir Crit Care Med\u003c/em\u003e 1997; 155: 364–370. [PMID: 9001337 DOI: 10.1164/ajrccm.155.1.9001337]\u003c/li\u003e\n\u003cli\u003ePatel N, Patel M, Inja R, Krvavac A, Lechner AJ. 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[PMID: 35616205 DOI: 10.1111/ped.15102]\u003c/li\u003e\n\u003c/ol\u003e"}],"fulltextSource":"","fullText":"","funders":[],"hasAdminPriorityOnWorkflow":false,"hasManuscriptDocX":true,"hasOptedInToPreprint":true,"hasPassedJournalQc":"","hasAnyPriority":false,"hideJournal":true,"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":"researchsquare","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":true,"externalIdentity":"","sideBox":"","snPcode":"","submissionUrl":"/submission","title":"Research Square","twitterHandle":"researchsquare","acdcEnabled":true,"dfaEnabled":false,"editorialSystem":"","reportingPortfolio":"","inReviewEnabled":false,"inReviewRevisionsEnabled":true},"keywords":"Plastic bronchitis, Bocavirus, Bronchoscopy, Atelectasis, Mediastinal emphysema, Subcutaneous emphysema","lastPublishedDoi":"10.21203/rs.3.rs-6496674/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-6496674/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"\u003cp\u003e\u003cstrong\u003eBackground: \u003c/strong\u003eBronchial cast disease often occurs as a complication following the Fontan procedure. In recent years, there have been an increasing number of reports in the literature on bronchial cast disease caused by pulmonary infections. However, the specific mechanisms underlying the development of bronchial cast disease are not yet fully understood.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eCase presentation: \u003c/strong\u003eIn this report, we present two cases of plastic bronchitis secondary to bocavirus infection. The patients were admitted to the hospital with fever, cough, and dyspnea as the main symptoms. Subsequent chest CT scans indicated pneumonia accompanied by bilateral neck and mediastinal emphysema, atelectasis, emphysema, and bronchial obstruction. The treatment primarily consisted of anti-infective therapy, symptomatic supportive care, bronchoalveolar lavage, and the removal of bronchial casts. After the extraction of bronchial casts and mucous plug-like secretions, both patients eventually entered a remission phase.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eConclusion: \u003c/strong\u003eHuman bocavirus-associated plastic bronchitis should be considered in children with significant pulmonary lesions. Bronchoalveolar lavage may be performed promptly to alleviate disease progression.\u003c/p\u003e","manuscriptTitle":"Plastic bronchitis complicated with mediastinal emphysema and subcutaneous emphysema due to bocavirus infection","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2025-06-30 08:52:41","doi":"10.21203/rs.3.rs-6496674/v1","editorialEvents":[{"type":"communityComments","content":0}],"status":"published","journal":{"display":true,"email":"[email protected]","identity":"researchsquare","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":true,"externalIdentity":"","sideBox":"","snPcode":"","submissionUrl":"/submission","title":"Research Square","twitterHandle":"researchsquare","acdcEnabled":true,"dfaEnabled":false,"editorialSystem":"","reportingPortfolio":"","inReviewEnabled":false,"inReviewRevisionsEnabled":true}}],"origin":"","ownerIdentity":"d276c177-41a7-46a0-8da3-edd9085db17d","owner":[],"postedDate":"June 30th, 2025","published":true,"recentEditorialEvents":[],"rejectedJournal":[],"revision":"","amendment":"","status":"posted","subjectAreas":[],"tags":[],"updatedAt":"2026-01-23T07:27:56+00:00","versionOfRecord":[],"versionCreatedAt":"2025-06-30 08:52:41","video":"","vorDoi":"","vorDoiUrl":"","workflowStages":[]},"version":"v1","identity":"rs-6496674","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-6496674","identity":"rs-6496674","version":["v1"]},"buildId":"8U1c8b4HqxoKbykW_rLl7","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}