The Puzzle of the Skin Patterns

Background: The pattern of distribution of skin diseases remains one of the most elusive problems in dermatology, particularly when multiple pathologies are involved and coexistence of patterns is present. Most skin diseases show a predilection for certain body areas and are located in characteristic patterns. Many dermatoses exhibit lesions in a segmental fashion concomitantly with disseminated patterns. Sometimes the sites of predilection are inexplicable. Objectives: The main purpose of this paper is to give an overview on the peculiar arrangement of cutaneous lesions in both congenital and acquired skin disorders as well as reactive phenomena in vulnerable areas, in order to better recognise them clinically and understand their pathogenesis. Methods: Based on personal observations and a review of literature, this paper summarises the basics in understanding the patterned distribution of skin lesions, highlights the significance of the lines of Blaschko and their relationship with mosaicism, and describes some of the reactive skin phenomena. Results: Skin mosaicism plays a crucial role in the distribution and arrangement of skin lesions, as demonstrated by recent advances in genetic research in an increasing number of various skin diseases.