The spectrum of fibrosing alopecias

Lichen planopilaris (LPP) is a primary lymphocytic cicatricial alopecia considered the most common cause of scarring hair loss in adults. It has been classified into three clinical variants: classical LPP, frontal fibrosing alopecia (FFA) and Graham Little-Piccardi-Lassueur syndrome. Classical LPP usually presents as a circumscribed cicatricial patch on the vertex and FFA as a band-like scarring alopecia of the frontotemporal hairline. Fibrosing alopecia in a pattern distribution (FAPD) and lichen planopilaris diffuse pattern (LPPDP) are two recently described subtypes of LPP that exhibit a diffuse involvement of the androgen-dependent region or the whole scalp, respectively. Classical LPP, FFA, FAPD and LPPDP share trichoscopic (cicatricial areas, absence of follicular openings, perifollicular erythema and hyperkeratosis) and histologic features (interface dermatitis involving follicular epithelium and concentric fibrosing around the isthmus and infundibulum). The remarkable clinical and histological overlap between these entities has led to the concept that these diseases exist along a spectrum. In the effort to identify classical LPP, FFA, FAPD and LPPDP with an umbrella term, we suggest to use ‘lichenoid alopecias’, as the distinguishing hallmark of these diseases is the lichenoid bandlike inflammatory infiltrate in the superficial dermis involving the infundibulum and isthmus of the hair follicle.