A New Subtype of Lichen Planopilaris Affecting Vellus Hairs and Clinically Mimicking Androgenetic Alopecia.

Background: Lichen planopilaris (LPP) is a follicular variant of lichen planus. A new subtype of LPP mimicking androgenetic alopecia (AGA) may be misdiagnosed. Inappropriate medical therapy or hair transplantation may exacerbate this subtype.

Objective: To introduce clinicopathologic findings of a new subtype of LPP that selectively affects vellus hair in the pattern of AGA.

Materials And Methods: In a cross-sectional study, 433 (66.6%) men and 217 (33.4%) women with alopecia who were candidates of medical treatment or hair transplantation were included. Gross and microscopic attributes of their diseases were investigated.

Results: Among the total of 650 patients, 58 (8.9%; 95% confidence interval, 6.7%-11.1%) patients, including 52 women and 6 men, had LPP. We identified a distinct category of LPP presenting with diffuse hair loss in the pattern of AGA with predominant terminal hair, significant decrease in vellus hair, and minute punctuate scars in histopathology. Vellus hair follicles were the main sites of involvement. Perifollicular fibrosis and mild fibrosis with lichenoid lymphocytic infiltration around infundibular area of vellus hair follicles were present.

Conclusion: There is a new form of LPP with clinical features similar to AGA. This form is histopathologically similar to LPP but selectively affects vellus hair follicles.