Idiopathic inflammatory myositis: Clinical, laboratory and therapeutic insights from a retrospective case series

of the work: This study aimed to characterize the clinical, laboratory, radiological, and therapeutic profiles of idiopathic inflammatory myopathies (IIMs) patients in an Egyptian cohort to enhance understanding and management of these conditions. Patients and methods: A retrospective case series was conducted on 99 IIM patients; 42 polymyositis (PM), 33 dermatomyositis (DM), 19 overlap syndrome, 5 cancer-associated myositis recruited from Mansoura Rheumatology and Immunology Unit (March 2023– January 2025). Data included demographics, clinical features, laboratory results, magnetic resonance imaging (MRI), and electromyography (EMG), and treatments. Results: The cohort was predominantly female (83.8 %), with a mean age of 36.6 years. Most patients (83.8 %) experienced diagnostic delays of less than 2 years. Proximal muscle weakness was present in 74.7 % of cases. In the DM patients, Gottron papules are the most common (∼70 %), followed by erythema (∼60 %), heliotrope rash (∼50 %), and the V sign (∼45 %). DM and overlap groups exhibited more frequent fever (48.5 % and 47.4 %, p = 0.006) and sclerodactyly was confined to overlap syndrome (15.8 %, p = 0.002). Overlap syndrome patients had higher arthritis frequency (68.4 %, p < 0.001). Laboratory analysis showed significantly lower creatine phosphokinase (CPK) levels in overlap syndrome (p = 0.001). MRI and EMG findings corroborated myopathic changes in most cases. Corticosteroids were the main therapy (76.8 %), with dexamethasone more frequently used in overlap and DM groups (p = 0.026). Conclusion: Idiopathic inflammatory myopathies manifests predominantly in females, typically with subacute proximal muscle weakness and systemic symptoms. Distinct clinical and therapeutic profiles were observed among PM, DM, and overlap syndromes, with overlap syndromes featuring higher arthritis rates.