Comparative Analysis of Immunopathological Features of Lichen Planopilaris and Female Patients with Frontal Fibrosing Alopecia

BACKGROUND: Frontal fibrosing alopecia (FFA) is a disorder characterized by progressive cicatricial alopecia (CA). Its classification as a clinical variant of lichen planopilaris (LPP) or as a unique disorder is controversial. The presence of Langerhans cells within the bulge area and the sebaceous epithelium and the presence of lymphocytic infiltrate in this area in CA have led to a series of hypotheses, although limited, about their development. To our knowledge, scarce is the literature demonstrating immunoanalytical studies comparing both disorders. OBJECTIVE: The authors sought to describe diagnostic findings, comorbidities, and immunopathological features of female patients with FFA as compared to LPP. MATERIALS AND METHODS: This retrospective single-center study included patients given the diagnosis of FFA or LPP. The LPP activity index was used to evaluate objective signs and subjective symptoms. Biopsy specimens were obtained from active, inflammatory areas of the scalp, and the inflammatory infiltrate intensity and quality were compared. Direct immunofluorescence for IgA, IgM, and IgG and immunohistochemistry to demonstrate the expression of CD1a, CD3, CD4, CD8, CD68, and 2,3-dioxygenase indoleamine were performed. RESULTS: Twenty female patients (10 patients with FFA and 10 patients with LPP) were included in the study. Histopathological findings evidenced reduced number of hair follicles and perifollicular fibrosis in both disorders. Immunofluorescence findings resulted positive in 50% of FFA cases and 40% of LPP cases. CONCLUSION: Although clinically different, our findings suggest that there are, to date, no histological or immunological findings that allow us to accurately separate these two forms of scarring alopecia, namely FFA and LPP.