Background Prognostic factors and long-term outcome including functional impairment of idiopathic inflammatory myositis (IIM) vary widely. In addition, the efficacy of immunosuppressive agents on clinical course of IIM, have not been well established.
Objectives To evaluate clinical course including relapse, functional impairment and mortality rate, and the efficacy of immunosuppressive agents in polymyositis (PM), dermatomyositis (DM), and amyopathic dermatomyositis (ADM).
Methods Clinical data of 88 IIM patients (33 with PM, 40 with DM, and 10 with ADM) who received induction therapy from April 2002 to July 2013 in Kobe University Hospital were collected from the medical charts. Survival rate were modeled Kaplan-Meier estimation. Functional impairment was evaluated with Health Assessment Questionnaire Disability Index (HAQ-DI).
Results Interstitial lung disease (ILD) was diagnosed in 63.1% of PM, 82.5% of DM, and all the ADM patients. Rapidly progressive ILD (RP-ILD) were found none of PM, 6% of DM, and 70% of ADM patients. Ten-year survival rate estimates of PM and DM were 79.3% and 76.2%, respectively. Half of ADM patients had a fatal clinical course of RP-ILD within 4 months after onset. Ten-year survival rate estimates without relapse were 74.5% for PM and 54.6% for DM. Immunosuppressive agents were used for 68.4% of PM, 61.5% of DM, and 90% of ADM patients. Predictors of poor outcome were male sex (analysis by Cox proportional hazards model, Hazard ratio (HR) 3.38, 95% confidence interval (CI) 1.20 to 9.48), ADM (HR 9.72, 95%CI 2.28 to 41.44), pneumomediastinum (HR 3.11, 95%CI 1.02 to 9.42), dysphagia (HR 3.27, 95%CI 1.12 to 9.50), and RP-ILD (HR 12.31, 95%CI 3.54 to 42.33). Patients positive for anti-Jo-1 antibody had a higher rate of recurrence (HR 3.52, 95%CI 1.33 to 9.36). Patients treated with immunosuppressive agents tended to have lower relapse rate than those without immunosuppressive agents (log-rank test, P=0.053). Patients with ILD associated with favorable physical function (multiple logistic regression analysis, Odds Ratio (OR) 12.07, 95%CI 1.91 to 126.54). Higher age patients had statistically high HAQ-DI (OR 0.19, 95%CI 0.04 to 0.75).
Conclusions Male sex, ADM, RP-ILD, pneumomediastinum and dysphagia predict the poor outcome, and anti-Jo-1 antibody-positive patients had a high relapse rate in IIM patients. Early administration of immunosuppressive agents may reduce the risk of relapse of IIM.
Disclosure of Interest None declared