Polymyositis, pulmonary fibrosis and autoantibodies to aminoacyl-tRNA synthetase enzymes. The clinical and laboratory features of 29 patients who had one of three anti-aminoacyl-tRNA synthetase autoantibodies, anti-Jo1 (histidyl-tRNA synthetase), anti-PL12 (alanyl-tRNA synthetase) or anti-PL7 (threonyl-tRNA synthetase) were analysed and compared with the findings of other published reports. These autoantibodies were found to be associated with a syndrome delineated by inflammatory myositis (24 patients) and pulmonary fibrosis (23 of 29), but also including inflammatory arthritis (26/29), keratoconjunctivitis sicca (17/29), sclerodactyly (21/29), Raynaud's phenomenon (27/29), hepatitis (8/29) and subcutaneous calcinosis (7/29). The most important clinical determinant of outcome in this group of patients was the severity of the interstitial pulmonary disease. No patient fulfilled the classification criteria for systemic lupus erythematosus, although 10 had autoantibodies to extractable nuclear antigens including Ro, La, RNP, and Sm, and two patients had anti-dsDNA antibodies. Although it seems unlikely that anti-aminoacyl-tRNA synthetase antibodies are directly responsible for causing disease, they may provide an important clue to the aetiology of this unusual syndrome. 