Autoantibodies in Idiopathic Inflammatory Myopathies

Autoimmune response to nuclear and cytoplasmic autoantigens is detected in about 60-80% of patients affected with idiopathic inflammatory myositis such as polymyositis (PM), dermatomyositis (DM) and inclusion body myositis (IBM). Some of the serum autoantibodies are shared with other autoimmune diseases (myositis-associated antibodies MAA) and some of them are unique to myositis (myositis-specific antibodies MSA). The MSA are found approximately in the 40% of PM and DM patients, whereas the MAA in the 20-50% of the patients. Myositis-specific or myositis-associated antibody detection in patients’ sera is useful in diagnosis and classification of these diseases, which are sometimes difficult to early recognize and correctly classify. Late diagnosis and mistaken classification of myositis postpone treatments leading to worse prognosis. Here we summarize major biochemical and clinical characteristics of known MAA and MSA, discussing also their possible role in the pathogenesis of myositis.