Vitiligo and psoriasis.

The concurrence of vitiligo and psoriasis in a single patient has previously been considered unusual. The clustering of seven such patients at our institution over the past 3 years prompted a literature review. Only eighteen well-documented cases could be found, although the incidence of psoriasis in larger series of vitiligo patients seems greater than the isolated case reports would indicate. The occasional tendency of psoriasis to start in, or remain confined to, areas of vitiligo, as well as a purported resistance of dark skin to psoriasis, has tempted some to conclude that depigmented skin may be predisposed to psoriasis. This tendency, however, was not observed in our seven cases or in the majority of previously reported cases. Immunologic phenomena abound in both vitiligo and psoriasis, and the incidence of immunologic phenomena may be increased in patients with both diseases. These phenomena, however, are too dissimilar to draw any conclusions regarding pathogenetic links between vitiligo and psoriasis. The workup of our seven cases, including complete blood cell count and differential, platelet count, VDRL, SMA 18, antinuclear antibodies, thyroid function studies, antithyroid antibodies, urinalysis, eye examination, and skin biopsies, did not further elucidate any possible relationship between vitiligo and psoriasis.