Pathogenesis of the idiopathic inflammatory myopathies

The inflammatory myopathies, commonly described as idiopathic, are a group of acquired diseases characterized by an inflammatory infiltrate of the skeletal muscle. On the basis of clinical and immunopathological features, three major diseases can be identified: dermatomiositis (DM), polymyositis (PM) and inclusion body myositis (IBM). Immunopathogenesis mechanisms are crucial for discriminating between the three different subsets of inflammatory myopathies. DM is a complement-mediated microangiopathy affecting skin and muscle. PM and IBM are T cell-mediated disorders, where CD8-positive cytotoxic T cells invade muscle fibres expressing MHC class I antigens. This article summarizes the main immunopathological markers. The impact of this new knowledge must be defined in relation to potential therapeutic targets for idiopathic inflammatory myopathies. (C) 2009 Elsevier Espana, S.L. All rights reserved.