Clinical spectrum and therapeutics in Canadian patients with anti-melanoma differentiation-associated gene 5 (MDA5)-positive dermatomyositis: a case-based review.

The objective of the study was to determine the clinical features and treatment course in Canadian patients with dermatomyositis (DM) associated with the anti-melanoma differentiation-associated gene 5 antibody (MDA5). A retrospective chart review of consecutive patients with anti-MDA5 antibody DM from two Canadian tertiary care centre between 2014 and 2018 was done. Twenty-one consecutive cases of anti-MDA5-positive DM were identified. Median age at diagnosis was 52 years, 71% Asians, predominantly Chinese, and 29% Caucasians. In this case series, all patients had either typical DM rash, or vasculopathy and ulceration unique to anti-MDA5-positive DM. 38% of the patients had rapid progressive (RP)-interstitial lung disease (RP-ILD), 33% had chronic ILD and 29% had asymptomatic ILD. Anti-Ro52 positivity was more prevalent in RP-ILD. Mortality was high in the RP-ILD group, with five deaths in eight patients. Lung transplant was life-saving intervention for three of the RP-ILD patients who survived. A review of the literature in treating RP-ILD associated with anti-MDA5 is presented. Although evidence is limited to small case series, cyclophosphamide (CYC) for refractory skin lesions, and CYC or mycophenolate mofetil plus a calcineurin inhibitor or rituximab (RTX) for RP-ILD appear efficacious. This is the largest North American case series of anti-MDA5-positive DM patients to date. There is a wide spectrum of clinical presentation of this entity. Survival is poor in those with RP-ILD; early aggressive immunosuppression and timely lung transplant were life-saving in our patients with RP-ILD.