Survival analysis of patients with dermatomyositis and polymyositis

To estimate the mortality rate and identify factors predicting survival in patients with polymyositis (PM) and dermatomyositis (DM). The medical records of 192 PM/DM patients who were treated at Chang Gung Memorial Hospital from 1999 through 2008 were retrospectively reviewed. The Taiwan National Death Registry (1999–2008) was used to obtain their survival status. Thirty-one (16.1%) of the 192 patients with PM/DM had an associated malignancy; 41 (21.4%) had interstitial lung disease (ILD). During the follow-up period, 55 (28.6%) patients died and the overall cumulative survival rate was 79.3% at 1 year, 75.7% at 2 years, 69.9% at 5 years, and 66.2% at 10 years. In univariate analysis, older age at PM/DM onset, anemia, thrombocytopenia, leukopenia, diabetes mellitus, ILD, cancer, and non-use of azathioprine were associated with higher mortality (p = 0.0172, 0.0484, <0.0001, 0.0008, 0.0001, 0.0036, 0.0010, and 0.0019, respectively). In multivariate Cox regression analysis, thrombocytopenia (hazard ratio [HR] 4.94, 95% confidence interval [CI] 2.60–9.37, p < 0.0001), diabetes mellitus (HR 2.57, 95% CI 1.38–4.80, p < 0.0001), cancer (HR 2.30, 95% CI 1.26–4.22, p = 0.0030), and ILD (HR 1.98, 95% CI 1.11–3.51, p = 0.0182) were positively associated with mortality. Use of azathioprine (HR 0.35, 95% CI 0.16–0.74, p = 0.0064) was negatively associated with mortality. This study confirmed the high mortality rate (28.6%) in PM/DM patients. Survival time was significantly reduced in patients with thrombocytopenia, diabetes mellitus, ILD, and cancer patients than in those without these conditions.