An Unusual Periungual Lesion

History A 56-year-old female presented with a 3-month history of a painful, subungual lesion arising from the distal nail bed of the left hallux ( Fig. 1 ). Her past medical history included sarcoidosis, for which she was receiving treatment with oral prednisolone. On examination she had a firm, hyperkeratotic lesion, which was approximately 6 mm in diameter underneath the left great toenail ( Fig. 2 ).