[Polymyositis and dermatomyositis]

This review summarizes the current progress in the clinical research on pathogenesis, diagnosis and treatment of polymyositis (PM) and dermatomyositis (DM). Recent studies on immunohistochemical and molecular findings of biopsied muscle tissues have shed light on pathogenetic mechanisms in myositis. Muscle imaging techniques such as ultrasonography and magnetic resonance imaging facilitate the assessment of the type (edema, inflammation, fat, and fibrosis), degree, and localization of these alterations. They are useful for the diagnostic evaluation and the assessment of treatment. Measurement of myositis-specific autoantibodies such as antisynthetases (anti-Jo-1 and others), anti-Mi-2, and anti-SRP is also useful for both diagnosis and classification of subgroup of patients with clinical, prognostic, and possible therapeutic implications. Novel treatment of refractory myositis includes methotrexate, cyclosporin, and intravenous high dose immunoglobulin. Anti-cytokine therapy will be a novel strategy for the treatment of myositis.