Increased expression of psoriasin (S100A7) and interleukin 17 (IL-17) in lesional skin in lichen planopilaris.

Introduction: Lichen planopilaris (LPP) is an inflammatory, primary scarring alopecia, however its pathogenesis is not completely elucidated. S100A7 is a multifunctional, antimicrobial protein with proinflammatory properties. Interleukin-17 (IL-17) is implicated in the development of various autoimmune skin diseases.

Aim: To determine the tissue expression of S100A7, S100A4 and IL-17 in LPP.

Material and methods: The immunohistochemical analysis was performed on biopsy specimens obtained from individuals with histologically confirmed lichen planopilaris (n = 23), alopecia areata (AA) (n = 11), and healthy controls (n = 14). The expression was evaluated using Zeiss Axio Imager A2 light microscope.

Results: The number of cells showing S100A7 expression was significantly higher in LPP lesional skin compared to AA lesional skin (p = 0.0002) and normal skin of healthy controls (p < 0.0001). The number of cells showing IL-17 expression was significantly higher in LPP lesional skin compared to normal skin of healthy controls (p < 0.0001) and the number of cells showing IL-17 expression was significantly higher in AA lesional skin compared to normal skin of healthy controls (p < 0.0001). The number of cells showing IL-17 expression was not significantly different in LPP lesional skin and in AA lesional skin (p > 0.05). The number of cells showing S100A4 expression was not significantly different in LPP lesional skin, AA lesional skin and in normal skin of healthy controls.

Conclusions: The results of our study suggest the possible role of S100A7 and IL-17 in the pathogenesis of LPP.