ObjectivesThe aim of this study is to analyze the prevalence of myositis-specific autoantibodies (MSAs) and to elucidate their associations with clinical features in Chinese patients with polymyositis (PM) and dermatomyositis (DM).MethodsTwelve subsets of MSAs including anti-Mi-2, anti-TIF1-gamma, anti-MDA5, anti-NXP2, anti-SAE1, anti-SRP, anti-Jo-1, anti-PL-7, anti-PL-12, anti-EJ, anti-OJ, and anti-HMGCR antibodies were tested. Four hundred and ninety-seven PM/DM patients were enrolled. Clinical features and laboratory data were collected. The frequency of MSAs and the correlations with clinical phenotypes were calculated by SPSS 21.0.ResultsMSAs were present in 65.4% in PM/DM patients. Anti-TIF1-gamma (14.3%), anti-MDA5 (12.5%), and anti-Jo-1 (10.1%) were the three commonest MSAs. Anti-SAE1 (OR 14.877, 95% CI 1.427-155.074), anti-SRP (OR 4.339, 95% CI 1.529-12.312) and anti-TIF1-gamma (OR 2.790, 95% CI 1.578-4.935) were associated with dysphagia. In contrast, anti-MDA5 (OR 0.356, 95% CI 0.148-0.856) might decrease the frequency of this manifestation. Interstitial lung disease (ILD) was observed more frequently in patients carrying anti-EJ (OR 14.202, 95% CI 1.696-118.902), anti-Jo-1 (OR 11.111, 95% CI 3.306-37.335), and anti-MDA5 (OR 3.109, 95% CI 1.578-6.128). On the contrary, anti-Mi-2 (OR 0.180, 95% CI 0.055-0.589), anti-TIF1-gamma (OR 0.163, 95% CI 0.080-0.333), and anti-HMGCR (OR 0.058, 95% CI 0.007-0.451) were protective factors against developing ILD. Anti-TIF1-gamma was an independent risk factor for cancer-associated myositis (OR 4.237, 95% CI 1.712-10.487).ConclusionsPM/DM patients had high frequencies of MSAs. Several MSAs were independent factors in determining unique clinical phenotypes.