Distinct Trichoscopic Features of the Sideburns in Frontal Fibrosing Alopecia Compared to the Frontotemporal Scalp.

The trichoscopic features of frontal fibrosing alopecia (FFA) have been described in the frontotemporal area, yet there is no data detailing the trichoscopic features of the sideburns, which can be the initial or exclusive area of involvement. In this retrospective cohort study, 236 trichoscopic images of the frontotemporal and sideburn area obtained via dry trichoscopy from patients with biopsy-proven FFA were examined by two independent researchers to determine the trichoscopic features of FFA in the sideburns. The images of the sideburns were compared to 44 trichoscopic images of 11 healthy volunteers with intact sideburns. Transparent proximal hair emergence surrounded by patches of paler smooth skin was the most prominent finding in the sideburns. Peripilar casts and peripilar erythema were rare in the sideburns compared to the frontotemporal area. Although less common, transparent proximal hair emergence was also seen in the sideburns of healthy controls, yet it was shorter and restricted to individual hairs. Early FFA presenting exclusively or mostly with sideburn involvement should not be missed due to absence of peripilar casts and peripilar erythema. Dermoscopy-guided biopsy obtained from hair shafts with transparent proximal hair emergence should be considered to make the diagnosis in this location.