Rituximab in the treatment of anti-MDA5 dermatomyositis-associated interstitial lung disease: a case-based literature review.

Interstitial lung disease (ILD) occurs with Idiopathic Inflammatory Myopathy (IIM) as a life-threating complication and is considered the most important prognostic determinant in this disease group. The antibody anti-melanoma differentiation-associated gene 5 (anti-MDA5) is associated to rapidly progressive ILD and poor overall survival. Rituximab (RTX) is becoming a drug of choice in management of refractory IIM-ILDs and rapidly progressive ILDs, despite its low level of evidence. We report the case of a 49-year-old man with new-onset clinically amyopathic dermatomyositis (CADM) with severe respiratory symptoms and mixed radiologic pattern of non-specific interstitial and organizing pneumonia, refractory to high dose corticosteroids and intravenous immunoglobulin and oxygen dependent. He was started on RTX 375mg/m2/week of which he completed 4 perfusions, with significant clinical improvement, and has been on maintenance to date with the rheumatology RTX standard protocol with no need for oxygen supplementation. RTX may represent a rescue therapy for patients with severe anti-MDA5-related CADM-ILD refractory to conventional immunotherapies. We identified reports of a total of 12 patients treated with RTX. Infection was the only reported adverse event (25%). Respiratory improvement (defined by symptoms, imaging or PFTs) was observed in 75% of patients, with 2 (17%) having achieved clinical remission. A total of three deaths occurred (25%), all resulting from ILD progression despite treatment. No therapeutic protocol with RTX seems to be more efficient nor associated with more adverse events than the others. Comparative studies are necessary.