For many years, a 49-year-old man has had an itchy rash on his right foot. It waxes and wanes with the seasons: worse during hot weather, better in the winter. He works in a hot warehouse where the dress code requires him to wear 9-inch boots.

The patient has treated the rash with many topical products, including clotrimazole, tolnaftate creams, and various powders. He has found that topical 1% hydrocortisone works best for relieving the itch.

On examination, there is redness, maceration, and mild edema in the webspace between the 4th and 5th toes, spilling onto the plantar forefoot in that area. KOH examination of scrapings from the affected area shows abundant fungal elements (hyphae).