Long-term survival of patients with idiopathic inflammatory myopathies: anatomy of a single-centre cohort.

Abstract

We aimed to characterise clinical manifestations, disease course, treatment, and mortality of IIM patients. We have also attempted to identify predictors of mortality in IIM. This was a retrospective single-centre study including IIM patients fulfilling the Bohan and Peter criteria. Patients were divided in 6 groups: adult-onset polymyositis (APM), adult-onset dermatomyositis (ADM), juvenile-onset dermatomyositis, 'overlap' myositis (OM), cancer-associated myositis, and antisynthetase syndrome. Sociodemographic, clinical and immunological features, treatment, and causes of death were recorded. Survival analysis and predictors of mortality was performed using Kaplan-Meier and Cox proportional hazards regression. A total of 158 patients were included with a mean age at diagnosis of 40.8±15.6 years. Most patients were female (77.2%) and Caucasian (63.9%). The most frequent diagnoses were ADM (35.4%), OM (20.9%) and APM (24.7%), respectively. Most patients (74.1%) were treated with a combination of steroids and one-to-three immunosuppressive drugs. Interstitial lung disease, gastrointestinal and cardiac involvement affected 38.5%, 36.5% and 23.4% of the patients, respectively. The survival rates at 5, 10, 15, 20 and 25 years of follow-up were 89%, 74%, 67%, 62% and 43%, respectively. During a median follow-up of 13.6±10.2 years, 29.1% have died, infection being the most common cause (28.3%). Older age at diagnosis (HR1.053, 95% CI 1.027-1.080), cardiac involvement (HR 2.381, 95% CI 1.237-4.584), and infections (HR 2.360, 95% CI 1.194-4.661) were independent predictors of mortality. IIM is a rare disease with important systemic complications. Early diagnosis and aggressive treatment of cardiac involvement and infections could improve survival of these patients.