Congenital, nevoid, and acquired skin diseases may follow lines of Blaschko, which are thought to reflect cell migration and clonal expansion during embryogenesis of the skin.1 This concept greatly relies on the hypothesis that disorders following Blaschko lines are caused by genetic mosaicism. The genetic mosaicism that manifests along Blaschko lines may result from Lyonization (random inactivation of 1 of the two X chromosomes in women) or somatic postzygotic mosaicism.2 Authentic genetic mosaicism was proved in only a few cases of Blaschko-linear nevoid or X-linked diseases.1,3,4 It is less obvious how the clonal hypothesis of Blaschko lines deals with acquired inflammatory diseases along the lines of Blaschko. The latter include, among others, such different diseases as lichen striatus, lichen planus, psoriasis, and lupus erythematosus. In this report, we were able to demonstrate for the first time genetic mosaicism in a Blaschko-linear inflammatory dermatosis.
Lipsker D, Cribier B, Girard-Lemaire F, Flori E, Grosshans E. Genetic Mosaicism in an Acquired Inflammatory Dermatosis Following the Lines of Blaschko. Arch Dermatol. 2000;136(6):805–807. doi: