Rapidly Progressive Polymyositis With Vasculitis: The Pivotal Role of Histopathology in Diagnosis and Management.

Idiopathic inflammatory myopathies are a heterogeneous group of inflammatory myopathies whose common feature is immune-related muscle injury. Polymyositis is a rare idiopathic inflammatory myopathy characterised by progressive proximal muscle weakness and muscle inflammation. Diagnosis can be challenging due to overlapping features with other neuromuscular conditions. This case highlights the pivotal role of histopathology in establishing a definitive diagnosis when clinical, laboratory, and electromyography findings were inconclusive. A 62-year-old woman presented with rapidly progressive proximal muscle weakness, dysphagia, and respiratory compromise. Muscle biopsy revealed definitive features of polymyositis with associated vasculitis, guiding targeted immunosuppressive therapy and resulting in a marked clinical improvement.