Clinical profile of anti-PL-12 autoantibody: Cohort study and review of the literature

Background: The antisynthetase syndrome consists of interstitial lung disease (ILD), arthritis, myositis, fever, mechanic's hands, and Raynaud phenomenon in the presence of an antisynthetase autoantibody, most commonly anti-Jo-1. It is believed that all the antisynthetases are associated with a similar clinical profile, but definitive data in this diverse group are lacking. The purpose of this study was to examine the clinical profile of anti-PL-12, an antisynthetase autoantibody directed against alanyl-transfer RNA synthetase. Methods: Thirty-one subjects with anti-PL-12 autoantibody were identified from the databases at the Medical University of South Carolina, the University of Pittsburgh Medical Center, Johns Hopkins Medical Center, and Brigham and Women's Hospital. The medical charts were reviewed and the following data were recorded: demographic information; pulmonary and rheumatologic symptoms; connective tissue disease (CTD) diagnoses; serologic autoantibody findings; CT scan results; BAL findings; pulmonary function test results; lung histopathology; and treatment interventions. Results: The median age at symptom onset was 51 years; 81% were women and 52% were African American. Ninety percent of anti-PL-12-positive patients had ILD, 65% of whom presented initially to a pulmonologist. Ninety percent of anti-PL-12-positive patients had an underlying CTD. Polymyositis and dermatomyositis were the most common underlying diagnoses. Raynaud phenomenon occurred in 65% of patients, fever in 45% of patients, and mechanic's hands in 16% of patients. Test results for the presence of antinuclear antibody were positive in 48% of cases. Conclusions: Anti-PL-12 is strongly associated with the presence of ILD, but less so with myositis and arthritis. Idiopathic ILD diagnosed as idiopathic pulmonary fibrosis may, in fact, be associated with anti-PL-12 and be a "forme fruste" of an underlying autoimmune disorder.