Pili Bifurcati

An uncommon transitory hair shaft dysplasia characterized by segmental duplication of the hair shaft: a ramification generates two parallel branches which fuse to form a single shaft again. Each branch is covered by its own cuticle.

Epidemiology

Prevalence is unknown, only a few cases have been reported.

Clinical description

Patients generally present with diffuse alopecia which can be more apparent in some areas. Hypopigmentation can be observed. This anomaly of the hair shaft occurs in normal hair, pili canaliculi, or monilethrix (see this term) and has been associated with the mosaic trisomy 8 syndrome (see this term), pseudomonilethrix type II or protein deficiency states. It can also be secondary to ulcerative colitis (see this term) and extensive bowel resection.

Etiology

Pili bifurcati is caused by a transient duplication of the papilla's tip during the anagen phase, leading to the transitory production a two complete shafts, in the same follicular matrix, that emerge through a single pilary canal. When the two papilla tips fuse, both parallel branches form a single shaft again. When the transient duplication of the papilla tip occurs repetitively during the anagen phase, a serie of bifurcation-fusion can be observed along the shaft. This situation is called pili multi-bifurcati. As a duplicated papilla tip can split again, a doubly bifurcated shaft may be observed: pili bi-bifurcati.

Diagnostic methods

Diagnosis is based on the trichogram analysis, which could show a high prevalence of dystrophic anagen hairs presenting the characteristic bifurcation(s), reduction in the shaft caliber and pigmentation and telogen effluvium.

Management and treatment

Management could include a protein complementation diet; mechanical procedures for care of the hair must be avoided.