Onychomycosis

(Tinea Unguium)

A fungal infection of the nails, most often caused by Trichophyton sp.

Onychomycosis is caused by dermatophytes, yeast, and nondermatophytic molds, depending on the geographic region and the patient's status. In temperate zones, dermatophytes are most commonly implicated, particularly Trichophyton sp.

The nails are yellow and thickened with distal separation of the nail plate from the nail bed (onycholysis). The diseased nail can serve as a reservoir of fungus, which can lead to recurrent tinea pedis, a known risk factor for cellulitis.

Diagnosis of onychomycosis is made clinically and confirmed by a potassium hydroxide preparation, fungal culture, or nail clipping for periodic acid-Schiff staining.

Although not all patients with onychomycosis require treatment, patients with pain, diabetes mellitus, or peripheral vascular disease should generally be treated with itraconazole 200 mg po daily or terbinafine 250 mg po daily. Treatment must continue until the affected nails have grown out, which usually takes 10 to 12 months in the elderly. Because these drugs are retained in the nails, patients can also be treated twice daily for 1 week of each month with comparable cure rates.