Moccasin-Variety Tinea Pedis

A 70-year-old man first noticed this skin condition when he returned from the South Pacific at the end of World War II. Over the years, the rash has itched only occasionally; however, during a recent spate of hot weather, the eruption became highly pruritic. Applications of an over-the-counter 1% hydrocortisone ointment exacerbated the condition.

On examination, a florid, papulosquamous, dry eruption with well-defined borders was evident around the rims of both feet. No interdigital involvement was noted. A potassium hydroxide preparation of scrapings from a lesion's border was markedly positive for fungal elements. Moccasin-variety tinea pedis was diagnosed.

The duration and nature of the condition made a cure unlikely; thus, the goal of treatment was disease control. Oral terbinafine, 250 mg/d for 1 week, and twice-daily application of terbinafine cream were prescribed. The patient was told to avoid corticosteroids, which exacerbate dermatophyte infections.

Moccasin-variety tinea pedis is usually caused by Trichophyton rubrum. This infection tends to be chronic, looks like dry skin, and often does not bother the patient. Careful examination reveals the well-defined, scaly border. In addition, the sole of the affected foot often has a powdery dry look with a fine scale that appears to accentuate the skin lines. Onychomycosis is often a concomitant condition. The differential diagnosis for moccasin-variety tinea pedis includes contact dermatitis; eczema; chronic irritation, as from ill-fitting shoes; and psoriasis.