Clinicopathological characteristics of fibrosing alopecia in a pattern distribution: a single‐center, retrospective study.

Background: Fibrosing alopecia in a pattern distribution (FAPD) is a distinct entity of primary cicatricial alopecia (PCA), mimicking diffuse hair loss of androgenetic alopecia (AGA) with trichoscopic and histopathologic features of both AGA and lichen planopilaris (LPP). Methods: Clinical, demographic, and histopathological data of 20 FAPD patients were retrospectively collected. Results: All patients presented with female pattern hair loss with a median Sinclair grade of 3. Trichoscopic findings revealed hair diameter variability (20/20), perifollicular erythema (mild 7/20, moderate 11/20, severe 2/20), peripilar casts (none 2/20, mild 12/20, moderate 5/20, severe 1/20), and loss of follicular ostia (+12/20, ±7/20, −1/20). Histopathologic examination revealed perifollicular lymphocytic infiltration at the infundibulum or isthmus level and an increase of vellus‐like hairs. All cases showed interface dermatitis with concentric perifollicular lamellar fibrosis and follicular scars. Infundibular or isthmic infiltration of mast cells was found. Conclusions: The uniqueness of our study lies in perifollicular mast cells and discovering that the young population is at higher risk than previously thought. Clinicopathological features of FAPD were identified, filling the void of much‐needed details for FAPD diagnosis tailored to the Chinese population. [ABSTRACT FROM AUTHOR]