[Nevus of the arrector muscle of hair]

We report on a 14-year-old boy who, at the age of 6 months, developed groups of pin head-sized protuberances on a bay leaf-shaped area of the skin above and below the left clavicle. These skin eruptions become more prominent in response to heat and cold, but cause no complaints. The histological picture shows longitudinal and cross sections of mm. arrectorum pilorum in large numbers.