Lines of Blaschko

The pattern assumed by many different nevoid and acquired skin diseases on the human skin and mucosae. The cause of the pattern of Blaschko lines is unknown; they do not follow nerves, vessels, or lymphatics. The lines described by these conditions not only did not correspond to any known anatomical basis, but were remarkably consistent both from patient to patient and even from one disease to another. The lines may represent a clinical expression of a genetically programmed clone of altered cells, perhaps first expressed during embryogenesis.