Pili Trianguli Et Canaliculi Is a Defect of Inner Root Sheath Keratinization

A 4-year-old Caucasian girl with pili trianguli et canaliculi exhibited unique ultrastructural changes, including tonofilament-desmosomal detachment and tonofilament clumping within inner root sheath cells. These findings suggested that the hair anomaly in this condition might be due to a compromised cytoskeleton, leading to configurational changes in the inner root sheath. Despite these changes, keratinization of the inner root sheath still occurred, which typically precedes the keratinization of the hair shaft. Therefore, the abnormally configured inner root sheath influenced the surface characteristics of the hair shaft in pili trianguli et canaliculi.