Pathology and Biology of Inflammatory Myopathies

T he idiopathic inflammatory myopathies (IIMs) are an important heterogenous group of potentially treatable acquired disorders. On the basis of clinical, histological and immuno-pathogenic features, three distinct subsets are recognised: dermatomyositis (DM), polymyositis (PM) and sporadic inclusion-body myositis (IBM). An accurate diagnosis is important, given the potential toxicity associated with the immunotherapy used to treat these disorders. A wide array of histochemical and immunocytochemical stains are used to investigate cases. This review outlines the clinical features, pathology and recent advances in the pathogenesis and treatment of IIMs, with a special emphasis on the role of muscle biopsy in their diagnosis and management.