Idiopathic Inflammatory Myopathies: A Comprehensive Review of Pathogenesis, Diagnosis, and Management

Abstract

Introduction: Idiopathic Inflammatory Myopathies (IIM) are a heterogeneous group of rare autoimmune disorders characterized by muscle inflammation. The classic presentation involves proximal and symmetrical muscle weakness, with the exception of Inclusion Body Myositis (IBM), which typically presents with distal and asymmetric weakness. This review aims to provide a comprehensive update on the clinical features, diagnosis, and management of IIM.

Discussion: The diagnosis of IIM is established through a combination of clinical examination, laboratory findings (elevated creatine kinase and specific autoantibodies), electromyography (EMG), and muscle histopathology. Extramuscular manifestations are common and may include Interstitial Lung Disease (ILD), pathognomonic skin rashes in Dermatomyositis (DM), and systemic or articular involvement. Furthermore, certain subtypes, particularly DM, are associated with an increased risk of malignancy. Treatment strategies predominantly rely on immunosuppressive therapy. First-line agents often include corticosteroids combined with methotrexate or azathioprine, while resistant cases may require mycophenolate mofetil, rituximab, or cyclophosphamide.

Conclusion: IIM can be distinctively classified into Dermatomyositis (DM), Polymyositis (PM), Necrotizing Autoimmune Myopathy (NAM), and IBM. While immunosuppression is effective for most forms, IBM remains a therapeutic challenge due to its complex pathogenesis and resistance to standard treatments. Continued research into novel therapeutic agents is justified to improve patient outcomes.