Tinea incognito

A 57-year-old man with a 20-year history of type 2 diabetes mellitus presented with a 1-year history of itchy rashes on both knees.He reported trying to treat the rashes with over-the-counter topical steroids on and off for the preceding 6 months.Physical examination revealed well-to ill-defi ned erythematous plaques with overlying papules and pustules in an annular pattern on both knees (Figure 1).Yellow-black discoloration, distal onycholysis, and dystrophy was noted on all of his toenails (Figure 2).Microscopic study of a potassium hydroxide preparation of scrapings from the active borders of the lesions on his knee was positive for dermatophytes.