53-Year-Old With Spreading Rash

A 53-year-old man presents to urgent care concerned about a spreading rash underneath his arms for the past 3 weeks. He initially thought it was an allergic reaction to a new deodorant, but the rash persisted after stopping the deodorant. The rash is not itchy. The patient has a history of type 2 diabetes. On examination, a broad, well-demarcated, thin, scaly plaque is seen extending from the lateral chest over the axilla to the upper arm.

View the image above and consider what your diagnosis and next steps would be. Resolution of the case is described on the following page.