Anti-MDA5 Antibody Dermatomyositis Overlap with Systemic Lupus Erythematosus: A Case Report and Review of the Literature

Background: Dermatomyositis (DM) is an autoimmune connective tissue disease that primarily targets the muscle, skin, and lungs. Many patients have autoantibodies that correspond to distinct clinical phenotypes. Melanoma differentiation-associated gene 5 (anti-MDA5) antibody, a specific antibody that targets the melanoma differentiation-associated gene 5 (MDA5), has been reported in DM cases and is significant for a distinct cutaneous presentation and rapidly progressive interstitial lung disease. Objective: Herein, we describe a patient with DM with a positive anti-MDA5 antibody and characteristic clinical phenotype, who subsequently developed coexisting systemic lupus erythematosus (SLE). A diagnosis of SLE was supported by his clinical phenotype, positive serologies, hypocomplementemia, and progression to glomerulonephritis and lupus cerebritis, features of which fulfilled the American College of Rheumatology criteria for SLE. Conclusion: DM is known to overlap with other autoimmune diseases, including SLE, and coexistence can lead to a wide variety of clinical presentations. SLE overlapping with anti-MDA5 positive DM may present with distinct clinical features.