High early mortality in idiopathic inflammatory myopathies: Results from the inception cohort at a tertiary care centre in northern India

Objectives: We determined the mortality along with the proportion of disease related adverse events measured individually and by a composite adverse outcome (devised by including deaths, disability, relapses and minimal response) and its predictors in an inception cohort of idiopathic inflammatory myopathies (IIM).

Methods: IIM from the MyoCite cohort (December 2017-19) were reviewed for early outcomes (mortality, IMACS core set). Comparisons were drawn between those meeting the primary and secondary outcomes.

Results: Of 70 patients [62 adults, M:F = 1:4.8, age 43 (28.5-51) and eight children, M:F = 1:1, 14.5 (8.8-16)], dermatomyositis (DM) was the most common subset [29 (41.4%) adults; 7 (87.5%) children]. Over 10 (4-15) months, 10 (15.2%) died and four polymyositis were reclassified. One-year survival for anti-melanoma differentiation antigen 5 (MDA5) subtype was 30% and anti-synthetase syndrome (ARS) subtype was 75%. Overall, lower respiratory infections were the most common cause of death [n = 3 (30%)] followed closely by malignancy and rapidly progressive interstitial lung disease (RP-ILD). Amongst survivors, a major IMACS response was recorded in 54.5% adults and 100% children. Thirty per cent suffered from moderate to severe disability and 16.7% experienced relapses. Overall, two-thirds accrued the composite adverse outcome. On multivariate analysis, older age and anti-MDA5 predicted mortality. Arthritis, rash and positive ANA reduced and anti-MDA5 increased the risk for the composite adverse outcome.

Conclusion: Indian patients with IIM suffer high early mortality attributable to infection, cancer and RP-ILD, calling for high vigilance post diagnosis. Autoantibodies and certain clinical features identify risk for composite adverse outcomes.