The line patterns of the skin and their dermatoses

Knowledge of the line patterns of the skin represents a key competence for every dermatologist. Four main groups of line patterns are relevant: Langer lines, dermatomes, Blaschko lines and exogenous patterns. Langer lines mark the direction of least skin tension and are diagnostically important for some exanthematic skin diseases. The thoracodorsal manifestation of Langer lines has been highlighted as the christmas tree pattern. Dermatomes are skin areas innervated by sensory spinal nerves. Skin diseases with neuronal pathogenesis follow this pattern. Blaschko lines are cutaneous manifestations of genetic mosaics that arise during embryogenesis. Exogenous linear patterns are caused by external factors.

The following discusses both dermatoses that primarily occur in these patterns and skin diseases that secondarily follow or spare these patterns through mechanisms of attachment (such as the Köbner phenomenon, Renbök phenomenon or isotopic reaction).