Tinea Pedis (Athlete's Foot)
Tinea pedis is the most common dermatophytosis because moisture resulting from foot sweating facilitates fungal growth. Tinea pedis may occur as any of 4 clinical forms or in combination:
Chronic hyperkeratotic tinea pedis due to Trichophyton rubrum causes a distinctive pattern of lesion, manifesting as scaling and thickening of the soles, which often extends beyond the plantar surface in a moccasin distribution. Patients who are not responding as expected to antifungal therapy may have another less common cause of plantar rash. Differential diagnosis is sterile maceration (due to hyperhidrosis and occlusive footgear), contact dermatitis (due to type IV delayed hypersensitivity to various materials in shoes, particularly adhesive cement, thiuram compounds in footwear that contains rubber, and chromate tanning agents used in leather footwear), irritant contact dermatitis, and psoriasis.
Chronic intertriginous tinea pedis is characterized by scaling, erythema, and erosion of the interdigital and subdigital skin of the feet, most commonly affecting the lateral 3 toes.
Acute ulcerative tinea pedis (most often caused by T. mentagrophytes var. interdigitale) typically begins in the 3rd and 4th interdigital spaces and extends to the lateral dorsum and/or the plantar surface of the arch. These toe web lesions are usually macerated and have scaling borders. Secondary bacterial infection, cellulitis, and lymphangitis are common complications.
Vesiculobullous tinea pedis, in which vesicles develop on the soles and coalesce into bullae, is the less common result of a flare-up of interdigital tinea pedis; risk factors are occlusive shoes and environmental heat and humidity.
Diagnosis of tinea pedis is usually obvious based on clinical examination and review of risk factors. If the appearance is not diagnostic or if the infection manifests as hyperkeratotic, ulcerative, or vesiculobullous, a potassium hydroxide wet mount is helpful.
Differential diagnosis of tinea pedis includes
(See table: Options for Treatment of Superficial Fungal Infections*.)
The safest tinea pedis treatment is topical antifungals, but recurrence is common and treatment must often be prolonged. Alternatives that provide a more durable response include itraconazole 200 mg orally once a day for 1 month (or pulse therapy with 200 mg 2 times a day 1 week/month for 1 to 2 months) and terbinafine 250 mg orally once a day for 2 to 6 weeks. Concomitant topical antifungal use may reduce recurrences.
Moisture reduction on the feet and in footwear is necessary for preventing recurrence. Permeable or open-toe footwear and sock changes are important especially during warm weather. Interdigital spaces should be manually dried after bathing. Drying agents are also recommended; options include antifungal powders (eg, miconazole), gentian violet, Burow solution (5% aluminum subacetate) soaks, and 20 to 25% aluminum chloride solution nightly for 1 week then 1 to 2 times/week as needed.
Tinea pedis is the most common dermatophytosis because moisture resulting from foot sweating facilitates fungal growth.
Consider the diagnosis if patients have lesions of the toes and/or feet that are intertriginous, ulcerative, hyperkeratotic, or vesicobullous.
Also consider dyshidrotic eczema, palmoplantar psoriasis, and allergic contact dermatitis.
Treat using topical and occasionally oral antifungals as well as drying measures.