More Than Skin Deep: Diffuse Calcinosis Mimicking Malignancy in Refractory Adult-Onset Dermatomyositis With Anti-transcription Intermediary Factor 1-Gamma (Anti-TIF1-γ) Positivity.

Dermatomyositis is a systemic autoimmune condition characterized by proximal muscle weakness and characteristic cutaneous manifestations, and it carries an increased risk of malignancy. Calcinosis cutis represents a recognized complication, more commonly seen in juvenile disease but occasionally occurring in adults, where it may present with atypical or extensive involvement. We present a patient with dermatomyositis who developed extensive calcinosis with atypical clinical features that raised concern for an underlying malignancy. Clinical evaluation, laboratory studies, and imaging were performed to assess disease activity and exclude alternative etiologies. The patient was managed with immunosuppressive therapy, with subsequent clinical improvement. This case highlights the diagnostic challenges associated with calcinosis in adult dermatomyositis and underscores the importance of careful evaluation to distinguish inflammatory disease manifestations from malignancy-related processes.