Histopathological differential diagnosis of frontal fibrosing alopecia and fibrosing alopecia in a pattern distribution

Funding sources: none. Conflicts of interest: the authors declare they have no conflicts of interest. Dear Editor, Frontal fibrosing alopecia (FFA) and fibrosing alopecia in a pattern distribution (FAPD) are forms of primary cicatricial alopecia, classified as subtypes of lichen planopilaris.1, 2 FAPD and FFA may present with clinical overlap and similar histopathological and dermoscopic features.1 Parietal scalp involvement with frontal hairline recession can obscure the clinical delineation between FAPD and FFA. The aim of this study was to establish whether FAPD can be differentiated from FFA by histopathological analysis. We conducted a cross‐sectional analysis of biopsies from 43 women, all with a previous classical diagnosis of FAPD or FFA.1–4 All samples had horizontal sections in haematoxylin and eosin stain. Anisotrichia (hair fibre diversity) was present only in patients with FAPD. Twenty‐one histopathological markers were critically compared and contrasted. Analysis of nonparametrically distributed data was performed using the Mann–Whitney U‐test, and Person's χ2‐test was used to measure association. The research complied with Good Clinical Practice guidelines and was approved by an institutional review board.