[Woolly hair nevus].

The author describes a case of "Woolly Hair Nevus" in a four years old white boy. The patient presents "Woolly Hair" in three circunscribed areas of the scalp since the age of ten months, and "nevus unius lateris" on the left arm and back of the neck since the age of eight months. The pathology of one of the localized areas of "Woolly Hair" is normal in what respects the hair follicle. Optical microscopy of the hair shaft of the involved areas shows reduced diameter and in two of them Trichonodosis. In some, the hair shaft is twisted in its own axis.