Folliculitis decalvans has a heterogeneous microbiological signature and impaired immunological response.

Background: Folliculitis decalvans (FD) is a rare primary neutrophilic scarring alopecia whose etiology has not been completely elucidated yet.Objective: To determine if the follicular microbiota residing in FD-affected hair follicles had a distinct microbiological signature and if an aberrant immune response was present in the pathogenesis of FD.Methods: We conducted a cross-sectional study of ten patients affected by FD. Trichoscopy-guided follicular biopsies were taken from affected and healthy scalp to identify the follicular microbiome using next-generation sequencing. We searched for microbiological biomarkers of FD-affected follicles using the linear discriminant analysis (LDA) effect size (LEfSe) tool. Additionally, peripheral blood mononuclear cells were obtained, and their cytokine production was quantified after incubation with pathogen-associated molecular patterns isolated from patients' biopsies and compared with healthy controls.Results: beta-diversity analysis showed statistically significant differences regarding bacteria comparing follicular microbiota of healthy and FD-affected hairs. Ruminococcaceae, Agathobacter sp., Tyzzerella sp. and Bacteriodales vadin HA21 family were good predictors of disease status. IL-10, TNF-alpha and IL-6 levels were significantly decreased in patients after incubation with various strains of bacteria compared with controls.Conclusion: FD hair follicles have a specific heterogenous follicular bacterial microbiota signature. Additionally, these patients seem to have an impaired immunological response.

Automated summary

By studying the follicular microbiota and immune response of patients with folliculitis decalvans, it was found that the affected hair follicles have a distinct bacterial composition and the patients have an impaired immune response. These findings contribute to understanding the etiology and pathogenesis of folliculitis decalvans.