Long-standing Tinea Pedis

September 14, 2005
Joe Monroe, PA-C

A pruritic rash of unknown origin had been present on the dorsum of a 26-year-old woman's foot for several months. Despite oral antibiotic therapy and applications of antifungal creams and topical corticosteroids, the condition did not resolve.

A pruritic rash of unknown origin had been present on the dorsum of a 26-year-old woman's foot for several months. Despite oral antibiotic therapy and applications of antifungal creams and topical corticosteroids, the condition did not resolve.

An annular, erythematous, papulosquamous lesion with distinctly scaly advancing margins was noted. The results of a potassium hydroxide (KOH) evaluation were positive for hyphae; tinea pedis was diagnosed.

Because the infection was long-standing and had been treated with corticosteroids, both topical and systemic antifungal agents were given; econazole cream and oral terbinafine, 250 mg/d for 2 weeks, were prescribed. Within a month, the foot dermatophytosis cleared completely.

The failure to perform a KOH examination initially led to uncertainty about the correct diagnosis and, thus, resulted in inappropriate therapy. The use of corticosteroids makes fungal infections more difficult to diagnose and treat. The differential diagnosis of tinea pedis includes corticosteroid-responsive conditions, such as psoriasis, eczema, and contact dermatitis; a timely KOH evaluation rules out these disorders, confirms the fungal infection, and leads to appropriate treatment.