A 3-year-old boy was seen because of moderate hair loss. While the initial clinical appearance suggested trichotillomania or pili torti, history and examination of several hairs that were removed from the affected region showed that some of them exhibited multiple intermittent bifurcations of the shaft at irregular intervals. The parallel twin rami formed by the bifurcation subsequently rejoined to form a normal-appearing shaft. In portions of some affected hairs, longitudinal grooving of the shaft was observed. Light and electron microscopic examination, in addition to scanning electron microscopic examination of affected hairs, substantiated the initial impression that each ramus of the bifurcated segments was circumferentially invested with its own cuticle. This was not simple, splitting trichoptilosis, and the designation, pili bifurcati, has been applied to this newly described anomaly.
Weary PE, Hendricks AA, Wawner F, Ajgaonkar G. Pili BifurcatiA New Anomaly of Hair Growth. Arch Dermatol. 1973;108(3):403-407. doi:10.1001/archderm.1973.01620240053016