The precipitating antibody to an acidic nuclear protein antigen, the Jo-1, in connective tissue diseases. A marker for a subset of polymyositis with interstitial pulmonary fibrosis.

The clinical significance of antibodies to the Jo-1 antigen in connective tissue diseases was studied. Clinical diagnoses of 11 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 anti-Jo-1 antibodies were detected before the appearance of lung disease.