A Marker for a Subset of Polymyositis with Interstitial Pulmonary Fibrosis SHUNJI YOSHIDA, MASASHI AKIZUKI, TSUNEYO MIMORI, HAJIME YAMAGATA, SHINICHI INADA, and MITSUO HOMMAThe clinical significance of antibodies to the Jo-1 antigen in connective tissue diseases was studied. Clinical diagnoses of I1 patients who had anti-Jo-1 antibody were: polymyositis 8, dermatomyositis 1, and overlap syndrome 2 (polymyositis-systemic lupus erythematosus 1, polymyositis-scleroderma 1). All the patients who had anti-Jo-1 antibody showed interstitial pulmonary fibrosis, and in 2 patients antiJo-1 antibodies were detected before the appearance of lung disease.Identification of antinuclear antibodies with defined specificities has diagnostic and prognostic value in connective tissue diseases (1-3). Recent studies reveal the presence of several precipitating antibody systems in polymyositis-dermatomyositis (PM-DM) in which immunologic abnormalities were previously considered to be infrequent (4-8). However, the results from several laboratories indicate that these serologic reactions have considerable heterogeneity, and their mutual relationships and clinical significance remain to be clarified (8).We have reported two distinct precipitating