Squamous Cell Carcinoma Arising in Discoid Lupus Erythematosus of the Nail Unit.

Introduction: Discoid lupus erythematosus can affect periungual tissues leading to onychodystrophy. Squamous cell carcinoma can occur in persistent scars of discoid lupus; this rare occurrence has not yet been reported on the nail unit. Case presentation: we report a case of squamous cell carcinoma occurring on the distal phalanx of the thumb in a patient with longstanding periungual discoid lupus on several fingernails. Discussion: Periungual discoid lupus erythematosus is rare. The scars caused by this disease can very rarely develop into squamous cell carcinoma. This is the first report of this occurrence at the periungual tissues.