Lines of Blaschko

The lines of Blaschko represent a pattern followed by many skin disorders. We review the clinical and histologic features of X-linked, congenital/nevoid, and acquired skin diseases that follow these lines. We also include cutaneous disorders that have a linear distribution but do not follow Blaschko's lines. Finally, we differentiate Blaschko's lines from other patterns on the skin such as dermatomes and Langer's lines. Learning objective: At the conclusion of this learning activity participants should be able to identify typical characteristics of the lines of Blaschko and skin diseases that follow these lines and that distinguish them from other cutaneous patterns.