Clinical and Prognostic Factors Associated With Survival in Mexican Patients With Idiopathic Inflammatory Myopathies

Background Factors associated with survival in patients with idiopathic inflammatory myopathies are heterogeneous. Objective This study aimed to describe clinical and prognostic factors associated with survival in Mexican patients with idiopathic inflammatory myopathies. Methods Patients with dermatomyositis (DM) and polymyositis (PM) seen at a tertiary care center from 1985 to 2012 were included. Demographic and clinical characteristics, comorbidities, treatment, and the time to death were recorded. Patients with juvenile DM were excluded. Univariate and multivariate analyses were performed to identify factors associated with mortality. Results A total of 264 patients with DM and 69 patients with PM were studied. Patients with DM had lower levels of creatine phosphokinase, less cumulative dose of prednisone, higher frequency of dysphagia, and no difference in frequency of interstitial lung disease compared with patients with PM. Patients with DM had lower survival during the first 4 years of disease (80%; 95% confidence interval [CI], 0.74-0.85 vs 89%; 95% CI, 0.78-0.95; P = 0.03 log-rank). Respiratory failure due to pulmonary infection was the main cause of death in patients with DM; miscellaneous causes were responsible for death in patients with PM. Muscular strength (hazard ratio [HR], 0.48; 95% CI, 0.27-0.83; P = 0.01), platelet count (HR, 0.98; 95% CI, 0.98-0.99; P = 0.002), as well as ever use of methotrexate (HR, 0.21; 95% CI, 0.07-0.65; P = 0.007) and azathioprine (HR, 0.21; 95% CI, 0.06-0.68; P = 0.009) were independent factors associated with mortality in patients with DM; in those with PM, only cancer was associated (HR, 8.0; 95% CI, 1.4-43.9; P = 0.01). Conclusions Patients with DM had lower survival during the first 4 years of disease than patients with PM. Factors associated with mortality differed in both groups.