Comparing survival and clinical features of anti-MDA5 and anti-synthetase idiopathic inflammatory myopathy in a North American cohort

Introduction Anti-synthetase syndrome (ASyS) and anti-MDA5 dermatomyositis (DM) cause significant morbidity and mortality due to interstitial lung disease (ILD). While large cohorts of these groups have been studied in Asia and Europe, data on clinical features and mortality risk within North America is limited. We aim to compare the mortality and clinical features between patients with anti-MDA5 DM and those with ASyS in a North American myositis cohort to identify predictors of mortality. Methods A retrospective chart review was conducted in a large healthcare system. Patients were identified through specialty clinics, diagnosed with anti-MDA5 DM or ASyS by an expert clinician, and confirmed positive for anti-MDA5 or an ASyS antibody. Demographics, clinical features including baseline pulmonary function tests (PFTs) and high-resolution CT (HRCT), and treatment regimens were collected. Statistical analyses included t-test, Wilcoxon tests, Kaplan–Meier curves, and univariate Cox proportional hazards models. Results One hundred patients (50% with anti-MDA5 DM, 50% ASyS) were analyzed. Over a median follow-up of 7.4 years, 18 patients died (8 in the anti-MDA5 group, 10 in the ASyS group). The 10-year survival rates of the two groups were similar. Age predicted mortality ( p ≤ 0.001), but race, the presence of ulcerations, initial HRCT with >20% ILD, baseline percent predicted forced vital capacity <70%, or percent predicted diffusing capacity of the lungs for carbon monoxide <55% did not. Conclusion Patients with anti-MDA5 DM and ASyS had similar survival rates. Older age at diagnosis predicted increased mortality, while baseline HRCT and PFT features did not. Further studies are needed to understand the variation in survival among patients with anti-MDA5 DM.