C.2 An in-depth analysis of pediatric inflammatory myopathies: findings from a comprehensive tertiary care hospital

Background: Pediatric inflammatory myopathies (PIM) are a rare, heterogenous group of disorders requiring prompt diagnosis and treatment to reduce complications and improve long-term outcome. This study reviews the clinical characteristics, management, and outcomes in PIM. Methods: A retrospective analysis of pediatric patients diagnosed with PIM at CHEO from January 2009 to December 2023 was performed. Patient data, including age at symptom onset, diagnostic testing performed, treatment, and follow-up durations, were evaluated. Results: A total of 25 patients with juvenile dermatomyositis (JDM), overlap syndromes, and necrotizing myopathy (HMG-CoA reductase and anti-SRP myositis) were identified. Symptoms began at an average age of 8.37 years (1.10-14.11), with formal diagnosis occurring at 8.57 years (2.02-16.11). Initial symptoms included skin changes, muscle weakness, joint pain, and fatigue. Diagnosis involved laboratory testing (CK, myositis antibodies), muscle MRI, electromyography, and/or muscle biopsy. Treatments included corticosteroids, IVIG, and steroid-sparing agents (methotrexate, mycophenolate mofetil, rituximab, hydroxychloroquine). Follow-up averaged 4.23 years (range: 0.5 to 13). Most patients displayed only mild residual symptoms with the exception of an anti-SRP myositis patient who became wheelchair-dependent, requiring ventilatory support. Conclusions: Inflammatory myopathies require prompt treatment to prevent complications. Most patients require multiple treatment modalities, however with early diagnosis and treatment the majority of patients’ symptoms resolve.