Abstract
<b><i>Introduction:</i></b> Frontal fibrosing alopecia (FFA) is a relatively recently described scarring hair loss condition. Frontal hair recession is observed in a vast majority of patients; other scalp areas may be included. Assessment of hair loss progression in FFA remains challenging mainly due to difficulties in unambiguous determination of the hairline. Various patterns of scarring and subtle progression rate are among factors which make naked-eye observations of limited use. <b><i>Methods:</i></b> Trichoscopy of the frontal hairline with hair-to-hair matching was conducted in patients with FFA patients with disease progression and clinically stable hairline. Hair loss was assessed based on analysis of trichoscopy-derived follicular maps. A relative hair density loss was calculated, and the hairline recession equivalent (HRE) was proposed as a novel hair loss progression measure. <b><i>Results:</i></b> Two patterns of hair loss were observed: one with significant decrease of hair density within a width of 1 mm and one with diffuse loss within a width of 10 mm. <b><i>Conclusion:</i></b> The hair density profile may be a useful tool to characterize different disease progression patterns. The HRE is potentially a very accurate and sensitive parameter to quantify local hair loss progression in FFA.