A histologic review of 27 patients with lichen planopilaris.

BACKGROUND: Lichen planopilaris (LPP) is a potential trichologic emergency that can result in permanent scarring alopecia. Histopathology is a key component of the diagnostic work-up.

OBJECTIVE: To identify the key histologic features that characterize LPP in order to facilitate diagnosis, ultimately leading to improved patient outcomes.

METHODS: Scalp biopsy specimens from 27 confirmed cases of LPP were reviewed in a blinded fashion to determine diagnostically helpful histologic features.

RESULTS: Absence of arrector pili muscles and sebaceous glands, a perivascular and perifollicular lymphocytic infiltrate in the reticular dermis and mucinous perifollicular fibroplasia within the upper dermis with absence of interfollicular mucin, and superficial perifollicular wedge-shaped scarring were characterizing features.

LIMITATIONS: Sample size was limited, given that biopsy specimens were taken from lesions at varying stages of evolution and findings vary with disease stage.

CONCLUSIONS: This study confirms many previously reported histologic features and highlights new characterizing features of mucinous perifollicular fibroplasia.