Distinctive age distribution and hair loss pattern putatively highlighting uniqueness of Japanese cases of fibrosing alopecia in a pattern distribution.

Fibrosing alopecia in a pattern distribution (FAPD) is a unique entity which presents clinicopathological characteristics of both male/female pattern androgenetic alopecia (AGA) and lichen planopilaris (LPP). This entity was first reported in 2000 and its criteria was recently proposed. Etiopathogenesis of FAPD has been speculated to be immunological destruction involving miniaturized hair follicles but still remains elusive. To date, few Asian FAPD cases have been reported in the literature. In this study, Japanese FAPD cases were identified based on the aforementioned criteria and analyzed to delineate clinicopathological characteristics. By retrospectively revisiting medical records and clinical photographs, 24 Japanese cases comprising 17 women and seven men were diagnosed as FAPD. All male patients had disease onset by their early 30s, whereas most female patients had developed the condition in middle age or later. Their initial diagnoses prior to the diagnostic confirmation of FAPD were mostly LPP. Based on the clinical phenotypes, the cases were categorized into AGA and LPP types. These subtypes were characterized by foremost trichoscopic and histopathological findings of AGA or LPP, respectively. Unlike previously reported cases, our patients tended to manifest hair loss in both vertex and frontal to mid-scalp with minimal regression of anterior hairline, manifesting unique "parachute" pattern, which has been reported as a representative characteristic of East Asian AGA in the literature. Anti-inflammatory therapies seemed to be effective to deter hair loss but insufficient to achieve improvement. Further accumulation of the cases is necessary; however, these findings may provide additional pathophysiological insights into FAPD and highlight uniqueness of the etiology and clinical phenotype of Japanese FAPD putatively influenced by racial predispositions.