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Fungal Infections of the Nail and Skin

Dermatophyte infection, or tinea, appears in many forms, including tinea corporis and cruris, tinea pedis, tinea capitis, onychomycosis, and fungal folliculitis. Tinea usually appears as a scaly pruritic patch that expands over time. Dermatophyte infection of hair follicles or the scalp can cause chronic inflammatory lesions or scarring leading to permanent hair loss.

Diagnosis. Tinea is usually an erythematous patch, more or less discrete, with scale prominent at the advancing borders of the lesions. After time or inadequate treatment, the patches may clear but leave fungus in the hair follicles.

Tinea capitis occurs almost exclusively in children, and is more common in blacks. It may present as patchy alopecia with scale or as an inflamed, indurated plaque, called a kerion. More subtle cases may only show hair loss.

Onychomycosis is a disease of adulthood and is characterized by nail thickening and subungual hyperkeratosis, usually with normal nails alongside affected nails. The entire nail or more distal portions are dystrophic.

Therapy. Limited tinea of the skin is treated with topical antifungal preparations. Extensive tinea corporis, fungal folliculitis, and tinea capitis are effectively treated with griseofulvin, a fungistatic agent with a good safety profile. Folliculitis and tinea capitis must be treated at a higher dose, usually for six weeks. Inadequate treatment may result in ongoing follicular infection with subsequent relapse and scarring alopecia.

Treatment of onychomycosis is difficult. Griseofulvin, because it is only a fungistatic agent, must be continued.

Itraconazole has recently been approved for the treatment of onychomycosis. It avidly binds keratin and achieves high persistent fungicidal drug levels in the nail plate. Itraconazole 200 mg bid for one week for four monthly cycles appears to achieve higher drug levels and better cure rates, but this regimen has not yet been approved by the FDA.

Diagnostic and therapeutic challenges. Other dermatoses that are patch-like and scaly are frequently misdiagnosed as tinea and can lead to costly mistreatment. Nummular eczema and dyshidrosis (hand or foot eczema) are both common in adults and are often treated as fungus. A KOH preparation will avert these misdiagnoses. As mentioned above, topical therapy is sufficient for limited tinea; steroid-antifungal combinations increase the risk of relapse.