[The Jo-1 Syndrome--immunological findings and clinical manifestations].

El The Jo-1 syndrome is an autoimmune disease which is characterized by the presence of autoantibodies against the Jo-1 antigen. The designation Jo-1 is derived from the name of the first patient (John P.) who was tested positive for this antibody. This patient suffered from polymyositis and fibrosing alveolitis. The Jo-1 antigen was identified as histidyl-transfer-RNA synthetase present in the cytosol. The Jo-1 syndrome is a member of a family of autoimmune diseases, called anti-synthetase syndromes. These syndromes are characterized by autoantibodies directed against aminoacyl-transfer-RNA synthetases. The etiology of the Jo-1 syndrome is unknown. The most frequent clinical manifestation is myositis, which may present as polymyositis or dermatomyositis. In addition to muscle involvement, interstitial lung disease is frequently found and critical for the prognosis. Furthermore, symptoms of other autoimmune disorders such as polyarthritis may occur. Similar to polymyositis and dermatomyositis, the Jo-1 syndrome may present as myositis overlap syndrome. In these cases, antibodies against U1-RNP are detected. The Jo-1 syndrome responds to treatment with corticosteroids and, if necessary, azathioprine, methotrexate or cyclophosphamide. The clinical manifestations of the Jo-1 syndrome are illustrated by two clinical cases.