Localized Darier's disease in a Blaschkoid distribution: two cases of phenotypic mosaicism and a review of mosaic Darier's disease.

Darier's disease is a rare autosomal dominant genodermatosis. Characteristic skin and nail changes consist of bilateral crusted red-brown papules and plaques in a seborrheic distribution, and V-shaped nicking or longitudinal ridging of the nails. In limited cases, a segmental distribution of this disease may be present in which localized lesions, found along the lines of Blaschko, are otherwise indistinguishable from those of generalized Darier's disease. Genomic mosaicism in localized lesions of Darier's disease is a new concept that was recently demonstrated in individuals of mosaic phenotypes. Both type 1 and type 2 mosaic phenotypes have been reported. We report two cases of type 1 localized Darier's disease in a Blaschkoid distribution and review the genetic implications of phenotypic mosaicism within the field of Darier's disease.