Pityriasis (tinea) versicolor, which occurs in hot, humid tropical regions and appears with greatest frequency in young adults, is caused by a normally commensal yeast, Malassezia furfur. Slowly spreading white or yellow-brown scaly plaques interspersed with depigmented areas appear on the trunk, buttocks and limbs, and rarely on the face. The active lesions appear dark in light-skinned persons, but in those with darker skins they may be pale and, if left untreated, they may leave hypopigmented patches.

Treatment

Application of sodium thiosulfate, 25% lotion, twice daily for 4 weeks should be started promptly. This is usually helpful, although areas of depigmentation remain long after completion of successful treatment. However, relapses are common, probably because much of the infected area may appear normal and be left untreated. Better results have been reported with topical applications of selenium sulfide. A thin layer of undiluted 2.5% detergent-based suspension should be applied at bedtime to the trunk, groin, upper limbs and axillae, and rinsed off after 5-15 minutes. Treatment should be repeated after 3 and 6 days. An alternative to selenium sulfide is salicylic acid. Initially a thin layer of the 2% ointment or paste is applied daily. The concentration is progressively increased to a maximum of 6%, and applications are continued until a satisfactory remission is obtained. Ketoconazole, 2% cream, applied once or twice daily for several weeks, is also usually effective. A single oral dose of 400 mg or a dose of 200 mg daily for 5 consecutive days is also reported to be effective.