B63-04 Noninfectious Bronchiolitis Obliterans in Childhood Autoimmunity: A Case of Therapeutic Response and Pulmonary Recovery

Abstract Introduction Bronchiolitis Obliterans (BO) is a rare, severe, and irreversible obstructive lung disease caused by inflammation and fibrosis of the small airways, leading to fixed airflow limitation. In children, post-infectious BO—most often following adenovirus or other viral infections—is the most common form. In adults, BO may occur secondary to autoimmune diseases, either as a consequence of immunomodulatory therapy or the disease itself. We report a 9-year-old girl with overlap syndrome (arthritis and myositis features) who developed BO and showed significant improvement with immunomodulatory therapy. Case Presentation This 6-year-old female with overlap syndrome (OS) presented with features of juvenile idiopathic arthritis (JIA) and juvenile dermatomyositis (JDM) including malar rash, photosensitivity, Gottron’s papules, arthritis and poor weight gain associated with lymphocytic colitis. Serologic evaluation revealed a positive ANA, intermittently elevated aldolase, and the anti-P155/140 (TIF1-γ) antibody. She initially responded to methotrexate (MTX) but developed worsening arthritis after a period of non-compliance, prompting a dose increase. Shortly thereafter, she experienced progressive chest pain and dyspnea, leading to cessation of sports participation. Pulmonary function tests revealed a worsening obstructive pattern without bronchodilator response, and CT imaging evolved from findings suggestive of bronchial atresia to diffuse air trapping, mosaic attenuation, and decreased vascularity, consistent with bronchiolitis obliterans (BO). Although MTX-induced lung toxicity was initially suspected, maternal confirmation of non-adherence prior to symptom onset suggested autoimmune-related BO. Initiation of monthly pulse corticosteroids and intravenous immunoglobulin (IVIG) led to marked clinical improvement within three months, paralleled by significant gains in pulmonary function. Conclusion This case underscores the complexity and severity of BO as a rare pulmonary manifestation of autoimmune disease in pediatric patients such as OS. The absence of any preceding viral or bacterial infection, together with the serologic and clinical evidence of both JIA and JDM features, supports the hypothesis that the BO in this patient is autoimmune-mediated rather than post-infectious. Moreover, given that she had been off methotrexate for at least six months prior to the onset of respiratory symptoms, MTX-induced pulmonary toxicity is unlikely. Clinical vigilance and early imaging is vital in children with autoimmune diseases who develop unexplained respiratory symptoms. This case also highlights the critical role of medication adherence and the diagnostic challenges in distinguishing drug-induced pulmonary toxicity from disease-related complications. Ultimately, multidisciplinary collaboration and continued research into autoimmune-associated pulmonary disease in children are essential to enhance early recognition, optimize management, and improve long-term outcomes. This abstract is funded by: None