Alopecia areata universalis sparing nevus flammeus.

Alopecia areata is a common form of nonscarring hair disorder of unclear etiology. Cases with alopecia areata sparing congenital melanocytic nevi have been described. It is explained by the Renbök phenomenon or inverse Köbner phenomenon, which refers to normal hair growth in the psoriatic lesions observed in patients with psoriasis and alopecia areata. We report a 30-year-old man presenting with rapidly progressing alopecia areata universalis, which spared a large nevus flammeus on the left parietal scalp. Our case gives further evidence to the notion that nevus as genetic mosaic may show genetically determined resistance to alopecia areata.