The itchy patch of skin on this 60-year-old man’s forearm, beneath his watch, has troubled him intermittently for a year. It is unresponsive to topical medications, including tolnaftate cream and 1% hydrocortisone cream; the latter seemed to improve the condition initially, but with time, the patch grew larger and itchier.
The patient’s primary care provider believed the rash might be precancerous and prescribed 5-fluorouracil cream, which showed no benefit. The patient was then referred to a dermatologist, who performed a KOH examination. No fungal elements were found.
At that point, the patient decided to simply ignore the problem. That resolve ended when the itchiness increased—leading to his presentation today. He is in decent health but has had a kidney transplant and is taking the standard immunosuppressant (anti-rejection) medications.
A faintly pink, scaly rash is located on the patient’s forearm. It is unimpressive in appearance but very bothersome to the patient.
Despite the patient’s history, fungal origin remains a possibility, as does psoriasis. A punch biopsy is performed.
What is the diagnosis?