A 50-year-old man presents with complaints of a rash on his right leg that manifested 20 years ago. Although the rash is worrisome, he says the associated pruritus is worse. During the workday, he is able to ignore the itching—but the minute he gets home, he begins to scratch.
He knows the scratching is counterproductive in the long run, but the urge to do it is quite compelling. Sometimes he uses a wet washcloth; other times, he will actually use a hair brush to satiate the itching. The relief is intensely satisfying albeit short lived.
The rash has persisted despite multiple treatment attempts. Tried products include OTC moisturizers and antifungal creams, as well as prescription antifungal creams. None has had an effect.
The patient denies any other skin problems. He does recall having eczema as a child. Although that has long since resolved, he remains quite allergy prone and is particularly sensitive to airborne allergens—a trait that runs strongly in his family.
A pink, oval rash covers most of the patient’s right lateral calf. It has a thickened, faintly scaly surface that is uniform and sharply circumscribed. There is no increased warmth or tenderness on palpation. No lymph nodes can be felt in the right groin. A check of the patient’s knees, elbows, scalp, nails, and trunk show no sign of rash or other changes.
What’s the diagnosis?