Ingrown Hairs: A Recurrent Trichoscopic Feature in Scarring Alopecias

The document reports a retrospective analysis of 20 patients with primary scarring alopecia who presented with ingrown hairs observed through trichoscopy, a noninvasive technique for evaluating hair loss. The patients included 7 males and 13 females, with 8 of African descent and 12 Caucasian. Trichoscopy-guided biopsies in 4 cases showed hair follicles with thinned outer root sheaths transfixed by hair shafts, associated with a giant foreign body type reaction. The study suggests that the inflammation in primary scarring alopecias may lead to thinning of root sheaths, causing hair shafts to enter the dermis and provoke a foreign body reaction. This feature of ingrown hairs was not observed in 30 patients with non-cicatricial alopecias. The authors conclude that follicular damage in scarring alopecias is responsible for the recurrent finding of ingrown hairs, but acknowledge the study's limitations due to its retrospective nature and small sample size, suggesting the need for further research to determine the exact frequency of this feature in scarring alopecias.