Long‐Term Outcomes and Prognosis Factors in Patients With Idiopathic Inflammatory Myopathies Based on Myositis‐Specific Autoantibodies: A Single Cohort Study

Objective This study was undertaken to investigate the long‐term survival rates and prognostic factors in patients with idiopathic inflammatory myopathies (IIMs) based on myositis‐specific antibody (MSA) stratification. Methods Exactly 628 patients with an IIM were included. Kaplan‐Meier survival curves, univariate, and multivariate Cox regression were used to analyze the outcomes and risk factors. Results The cumulative 1‐, 5‐, and 10‐year survival rates for IIM patients overall were 91.4%, 82.8%, and 75.6%, respectively. The survival rate in the MSA subset was significantly different ( P < 0.001). The 1‐ and 10‐year survival rates in the anti–melanoma differentiation–associated protein 5 (anti–MDA‐5)–positive subgroup were 79.5% and 58.5%, respectively, which were the lowest among all subgroups. The 10‐year survival rate of anti–signal recognition particle (anti‐SRP)–positive patients was the highest (96.4%). Independent risk factors that impacted the long‐term prognosis for IIM patients included rapidly progressive interstitial lung disease (RP‐ILD), malignancy, and elevated serum ferritin levels (hazard ratio [HR] 17.47, 20.36, and 9.15, respectively, P < 0.01), whereas disease duration was a protective factor (HR 0.27, P = 0.003). Among these subsets, the strongest independent risk factor for death in the anti–MDA‐5–positive subgroup was RP‐ILD (HR 3.4, P = 0.017). Malignancy was an independent risk factor in the anti–aminoacyl‐tRNA synthetase antibody–positive, anti–transcription intermediary factor 1γ–positive, and MSA‐negative subgroups (HR 46.69, 6.65, and 4.48, respectively; P < 0.001). RP‐ILD was also a risk factor in the prognosis of individuals in the MSA‐negative subgroup (HR 72.28, P < 0.001). Conclusion Despite favorable overall survival in patients with IIM, the anti–MDA‐5–positive subgroup had the highest mortality rate among all MSA subgroups, highlighting the distinctive prognosis for patients with different MSAs. RP‐ILD and malignancy are the most common causes of death in IIM patients.