Assessment of Mortality in Autoimmune Myositis With and Without Associated Interstitial Lung Disease

Purpose: Among patients with autoimmune myositis, associated interstitial lung disease (MA-ILD) is a known contributor of excess morbidity and mortality. Recent data on survival in idiopathic inflammatory myopathies originate primarily in Asia and Europe and vary widely. We sought to examine mortality in a large U.S. myositis cohort focusing in particular on the impact of associated ILD. Methods: A cross-sectional analysis of participants from the Johns Hopkins Myositis Center with autoimmune myositis (polymyositis [PM], dermatomyositis [DM], or clinically amyopathic dermatomyositis [CADM]) was conducted. The primary outcome assessed was all-cause mortality. Cumulative mortality rates were estimated using the Kaplan–Meier test; the Cox proportional hazards model was used to compare group differences in survival. Results: Eight hundred and thirty-one participants were included with a median follow-up time of 4.5 years. Four hundred thirty-eight (53 %) had PM, 362 (43 %) had DM, and 31 (4 %) had CADM. Ninety-four (11 %) participants had clinically evident ILD. Overall, 51 participants died (6 %). In those without ILD, the survival rates at 1, 5, and 10 years were 99, 95, and 90 %, respectively. In those with ILD, the survival rates at 1, 5, and 10 years were 97, 91, and 81 %, respectively. The risk of death was statistically significantly higher among participants with ILD compared to those without ILD (HR 2.13. 95 % CI 1.06–4.25; p = 0.03). Conclusions: We analyzed one of the largest known cohorts of patients with autoimmune myositis and found significantly higher mortality rates among those with clinically evident ILD compared to those without clinically evident ILD. Our results suggest that ILD remains an important and significant source of mortality in patients with inflammatory myopathies and as such should be screened for and treated aggressively.