Nummular Eczema: Don't Mistake it for a Fungal Infection

The multiple, uniformly scaly, coin-shaped, papulosquamous lesions shown here on the lower leg of a 61-year-old man had persisted for 3 months despite application of topical clotrimazole and 1% hydrocortisone. The rash involved only the legs and was variably pruritic. The patient had a long history of dry skin. Recently, he had begun to swim daily for exercise. Every day, he took long, hot showers and used highly perfumed bar soap. A potassium hydroxide preparation of scrapings from the lesions was negative for fungal elements. Joe Monroe, PA-C, of Tulsa, Okla, writes that these lesions are highly characteristic of nummular eczema-a reaction associated with dry skin that may be aggravated by soaps, frequent bathing, allergies, and certain medications. Exposure to winter weather and regular use of a hot tub are also well-known triggers. This rash is common, but it is frequently misdiagnosed as a “fungal infection.” Affected patients are often given multiple courses of antifungal therapy without success and are then referred to a dermatologist. Nummular eczema primarily occurs in middle-aged and elderly persons; the cause is unknown. The dorsum of the hand is the most commonly involved site; other frequently involved areas include the extensor aspects of the forearms, lower legs, flanks, and hips. The course is variable, but it is usually chronic.¹ Besides tinea, the differential diagnosis includes psoriasis, Bowen disease, and discoid lupus erythematosus (DLE). Psoriasis usually involves additional areas, such as the elbows and knees; patients often have a history of psoriatic eruptions. Bowen disease typically appears as a fixed, solitary lesion on sun-damaged skin. DLE is almost always triggered by sun exposure; the annular lesions have central clearing. Treatment of nummular eczema involves adequate skin moisturizing; use of nonirritating soaps; and reduced temperature, length, and frequency of showers and baths. The application of mid- to high-potency topical corticosteroid ointments may hasten resolution. Failure of this treatment indicates the need for a biopsy. This patient was successfully treated with clobetasol ointment.

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Habif TP. Clinical Dermatology: A Color Guide to Diagnosis and Therapy. 4th ed. Philadelphia: Mosby;2004:61.