[Myositis: current data on the classification, diagnosis and treatment].

The classification of idiopathic inflammatory myopathies has been refined with the characterization of new antibodies and their clinicopathological associations. The most widely used classification (Troyanov) defines pure polymyositis (PM) and dermatomyositis (DM), myositis overlap (presence of extra-muscular-extra-cutaneous manifestations or auto-antibodies), myositis associated to cancers and sporadic inclusion body myositis IBM). Overlap myositis are generally more severe and chronic than pure forms, and almost always require immunosuppressants. IBM remains difficult to treat, but immunosuppressants or immunoglobulins may be proposed, especially at the beginning of evolution.