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Document Details : Title: Inflammatory myopathies Author(s): CHERIN P Journal: Acta Clinica Belgica Volume: 59 Issue: 5 Date: 2004 Pages: 290-299 DOI: 10.2143/ACB.59.5.2050419 Abstract : Polymyositis (PM), dermatomyositis (DM) and sporadic inclusion body myositis (s-IBM) are three distinct idiopathic inflammatory myopathies (IIM), characterized by a common histological endomysial inflammation and distinct immune-mediated mechanisms (1,2). During the past decade there have been remarkable achievements in the immunopathogenesis of these myositis that laid the grounds for more effective therapeutic interventions In PM and s-IBM sensitized CD8+ cytotoxic T cells recognize as yet unidentified muscle antigens. The cytotoxic cells surround, invade and destroy non-necrotic muscle fibers that express class I MHC molecules (1, 2). Muscle fiber necrosis occurs by the exocytosis granule model, releasing toxic proteins, especially perforin and granzyme B (3). DM differs from the other two diseases clinically, because of the characteristic rash that accompanies or often precedes the muscle weakness, and the presence of an intramuscular microangiopathy, mediated by the complement C5b-C9 membranolytic attack complex, which leads to the destruction of endothelial cells, loss of capillaries, muscle ischaemia, muscle fiber necrosis and perifascicular atrophy (1, 2, 4). Dermatomyositis and polymyositis are considered to be responsive to immunosuppressive and immunomodulating therapies, in contrast to IBM, which is refractory to all treatment. |
