Objective The objective of this study was to describe the longitudinal disease course and pulmonary outcomes of North American patients with melanoma differentiation‐associated gene 5 antibody (MDA5 ab) associated dermatomyositis (DM). Methods Thirty patients with MDA5 ab DM were identified in a single center longitudinal cohort of 352 patients with idiopathic inflammatory myopathies. Longitudinal assessments of patient clinical and laboratory disease characteristics, pulmonary function tests (PFT), and high‐resolution computed tomography (HRCT) chest scans were conducted. Results Eighty percent (n=24/30) of MDA5 ab DM patients had ILD. The overall mortality was low 2/24 at a follow‐up of 4.0 ± 0.8 (mean±SD) years. At this follow‐up patients were receiving 3.1 ± 1.3 therapies, including 79% receiving IVIg, 58% rituximab, 67% mycophenolate, and 63% corticosteroids. In 18/22 surviving ILD patients who had 2‐year longitudinal follow‐up available at 1.8 ± 0.6 years, improvements of 16% and 17% in percent predicted (%pred) forced vital capacity (FVC) and diffusing capacity for carbon monoxide (DLCO) were noted. In 10/18 patients with additional long‐term follow‐up available (6.8 ± 3.4 years), improvements of 24% and 20% pred FVC and DLCO were noted. Levels of MDA5 ab, IL‐15 and paraoxonase 1 (PON1) enzyme activity correlated significantly with disease activity at baseline and longitudinally. Conclusions In a North American MDA5 ab DM‐ILD cohort treated with aggressive combination immunomodulatory therapy including predominantly mycophenolate, IVIg, and rituximab, disease mortality was low and lung function improved markedly. IL‐15, PON1, and MDA5 ab titers warrant further investigation as disease activity biomarkers in this high‐risk population.
Cheah et al. (Tue,) studied this question.