Psoralen therapy in vitiligo

Vitiligo is an idiopathic, acquired, circumscribed hypomelanosis, which is often associated with a positive family history. It is one of the most common leukodermas affecting approximately 1–4% of the world's population. 1 Vitiligo is characterized by discrete pale white macules, few or many in number that tend to enlarge centrifugally over time. In general, patients with vitiligo are healthy; however, the physical disfigurement perceived by those afflicted and those they confront often leads to social embarrassment and psychologic turmoil. 2 The characteristic histologic picture of vitiligo is the total absence of melanin and melanocytes in involved skin (Fig. 11-1). The epidermis and dermis are otherwise normal. The mechanism by which epidermis and/or follicular melanocytes disappear is not yet known. 3 Today there are three prevailing theories of the pathogenesis of vitiligo: the immune hypothesis, the neural hypothesis, and the self-destruction hypothesis. These three theories are not necessarily mutually exclusive. 1 Recent reports suggest that specific anti-melanocyte autoantibodies are present in most patients with vitiligo. 4,5 Their melanocytotoxicity in vitro suggests their active role in this disorder. The possibility that vitiligo corresponds to a syndrome and not to a single disease entity has been discussed. 1 In vitiligo the cosmetic disfigurement is due to the contrast between involved and uninvolved skin. One of the therapeutic options is to induce repigmentation of the vitiligo skin. For more than three thousand years, it is known that plants combined with natural sunlight can be used to treat successfully vitiligo. In Ancient Egypt and India, physicians and herbalists used the plant species Ammi majus Linnaeus in Egypt and Psoralea corylifolia L. in India for repigmentation of vitiligo. 1,6,7 In 1947 several crystalline compounds, including ammoidin (8-methoxypsoralen) and bergapten (5-methoxypsoralen), were isolated from the powder of Ammi majus L. 8 El Mofty 9 showed that 8-methoxypsoralen was useful in the treatment of vitiligo. Later, other psoralens, such as trioxsalen (4,5,8 trimethylpsoralen) were developed. Psoralen photochemotherapy is still the most successful (or less disappointing) current therapy involving the use of psoralens and subsequent exposure to long-wave ultraviolet radiation. Other photoactive compounds such as khellin 10–12 and hypericin 13–15 have also been tried.