Case report: malignant melanoma arising during drug therapy for vitiligo.

A 30-year-old white male developed cutaneous patches of depigmentation which were treated with Trioxsalen ingested before daily sunbathing. A darkly pigmented lesion which appeared three weeks later on his back was widely excised and classified as a low-grade malignancy. Although the treatment of vitiligo with plants containing photodynamically active compounds dates back as far as 1400 BC, the modern period of research began only in the 1930's leading to the development of oral psoralens, a coumarin derivative. In early tests, patients showed increased sunlight tolerance and repigmentation of vitiliginous areas. Although some patients have developed uveitis and vitiligo while being treated for melanoma, previous published reports deny any cutaneous malignancy arising during drug therapy of vitiligo. The associations between vitiligo and melanoma are discussed. The possible causative role of Trioxsalen in etiology of the case presented is discussed.