MKSAP Quiz: Several months of itchy, scaly feet
A 50-year-old man is evaluated for a several-month history of itchy, scaly feet. It has persisted despite the application of a moisturizing lotion. A physical exam reveals erythematous scaly patches on the sides of the feet and maceration between toes. What is the most appropriate treatment?
A 50-year-old man is evaluated for a several-month history of itchy, scaly feet. It has persisted despite the application of a moisturizing lotion. He has no significant medical history and takes no medications.
On physical examination, vital signs are normal. There are erythematous scaly patches on the sides of the feet and maceration between toes. Toenails are normal. Microscopic examination using potassium hydroxide preparation shows branching hyphae in the keratin (scale).
Which of the following is the most appropriate treatment?
A. Imidazole cream
B. Nystatin cream
C. Oral ketoconazole
D. Topical betamethasone and clotrimazole
MKSAP Answer and Critique
The correct answer is A. Imidazole cream. This content is available to MKSAP 18 subscribers as Question 64 in the Dermatology section. More information about MKSAP is available online.
Dermatophytosis or tinea of non–hair-bearing skin with limited involvement can be treated with imidazole cream applied once to twice daily for 2 to 4 weeks. Application should extend a few centimeters beyond the advancing border. For tinea pedis, the web spaces between the toes should be treated. Other topical agents including miconazole, clotrimazole, ketoconazole, ciclopirox, or terbinafine can also be used. Over-the-counter preparations are cost-effective options with good efficacy. Most infections will resolve but may recur and require retreatment. In immunosuppressed patients, recognition and treatment of superficial skin fungal infections is essential, as fungal infections can lead to epidermal breakdown and create a portal of entry for invasive pathogens. Tinea pedis is also a potential cause of recurrent bacterial cellulitis.
Dermatophytes do not respond to topical nystatin, which is used to treat infections caused by Candida species.
Oral antifungal therapy with terbinafine or an azole antifungal agent such as itraconazole or fluconazole may be necessary for treating tinea capitis, onychomycosis, Majocchi granuloma (a granulomatous response to dermatophyte infection in the dermis and hair follicles), or extensive infection. Oral ketoconazole no longer has an indication for superficial fungal infection because of severe and sometimes fatal idiosyncratic liver toxicity. In addition, ketoconazole is a potent inhibitor of CYP3A4 resulting in significant drug interactions. Prolonged use of ketoconazole also may result in adrenal gland suppression.
Combination therapy with potent topical glucocorticoids, such as betamethasone, and antifungal creams, such as clotrimazole, should be avoided because of an increased risk of treatment failures, development of skin atrophy with prolonged use, and increased cost without increased efficacy.
Key Point
- Treatment of tinea of non–hair-bearing skin includes topical antifungal agents such as imidazole, miconazole, clotrimazole, ketoconazole, ciclopirox, or terbinafine; topical nystatin is not effective, and oral ketoconazole should be avoided.