[Recent Developments in Myositis Syndromes]

Idiopathic inflammatory myopathies (IIM) are a rare and clinically polymorphic and heterogenous group of myositis syndromes. Myositis is part of a systemic autoimmune disorder with various extramuscular manifestations affecting skin, lungs, joints, esophagus and other organ systems. Most myositis patients have autoantibodies against non organspecific antigens. More than 20 different autoantibodies are known. They are associated with different clinical phenotypes of adult or juvenile dermatomyositis or myositis-overlap syndromes and different genetic markers. Pure polymyositis, if not a monosymptomatic manifestation of a systemic disorder, so far has no marker antibody and is an exclusion diagnosis. Sporadic inclusion body myositis (sIBM) has no extramuscular manifestations, cN1A antibodies are directed against muscle-derived antigen and are not highly specific for IBM.Myositis syndromes differ in histopathology. Patients with anti-synthetase-syndrome frequently have necrotizing perifascicular myositis with myonuclear actin inclusions.New classification criteria have been developed by the European (EULAR) and American (ACR) rheumatology societies and different outcome measurements for clinical studies are now available.There is still a lack of controlled therapeutic trials. However there is good consensus that glucocorticosteroids (GC) are necessary and effective to treat active myositis usually in combination with methotrexate or azathioprine. Rituximab is effective in GC-resistant myositis as well as high dose i. v. immune globulin (IVIG) in certain conditions.