Pili multigemini. Report of a case in association with cleidocranial dysostosis.

A patient with cleidocranial dysostosis developed extensive pili multigemini over the heavily bearded chin and cheek areas. Histological examination of serial sections revealed complicated follicular structures forming from two to as many eight hair shafts. Each hair is formed by a single branch of dermal papilla which is surrounded by all layers present in a normal follicle except for the outer root sheath cells. The outer root sheath surrounds the entire follicle. Irregularities in configuration of the hairs, longitudinal grooving and areas of bifurcation and re-adhesion of the hair shafts are demonstrated.