Seronegative dermatomyositis presenting with features of anti-MDA5 subtype.

Dermatomyositis is a chronic inflammatory disorder of muscles and skin, presenting with muscle weakness, characteristic rash, and classic serology findings. Histologically, cutaneous lesions show interface dermatitis with mild perivascular lymphocytic infiltrate and increased intradermal mucin. These findings are non-specific, and the diagnosis is based on clinicopathologic correlation and serology results. However, variation in clinical presentation, serology, and histology can make the diagnosis difficult and requires cognizance of uncommon findings that may serve as a clue to the diagnosis. Herein, we report such a case with unusual histologic features of vascular damage and deep dermal necrosis in a seronegative patient who presented with clinical features of anti-MDA5 variant of dermatomyositis.