Folliculitis decalvans (FD) is a chronic neutrophilic scarring alopecia which exact pathogenesis remains unknown. The recent report on the successful use of a novel anti-IL17 biologic agent in FD and the presence of IL-17-secreting mast cells in other types of scarring alopecias point to a distinct pathogenic mechanism in this disease. Our aim was to study and correlate the expression of IL-17 and mast cells in lesional and non-lesional FD scalp, using immunohistochemical techniques. Increased expression in IL-17 and mast cells was found in lesional scalp compared to non-lesional scalp areas (p<.05). A significant positive correlation between IL-17 and Mast cell Tryptase immunolabeling in non-lesional scalp (r=.64) highlights the role of IL-17-secreting mast cells in "normal-appearing" sites of FD. These findings suggest that targeting both IL-17 and mast cells may be potentially beneficial to better control the chronic inflammatory status of the disease specially in recalcitrant cases of FD.
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