Immunohistochemical evaluation of inflammasome expression in cutaneous lesions of mycosis fungoides and pityriasis lichenoides chronica

Mycosis Fungoides (MF) is the most common subtype of primary cutaneous T cell lymphoma. Pityriasis lichenoides is a skin disorder that is classified into acute and chronic types named pityriasis lichenoides et varioliformis acuta and pityriasis lichenoides chronica (PLC) respectively. Inflammasome is a part of natural immune system which has a multimeric structure consisting of the receptor, adaptor and effector protein that shows specificity for various ligands or activators. Five inflammasomes have been identified which are AIM2, NLRP1, NLRP3, pyrin, and NAIP/ NLRC4. After the activation of these inflammasomes, caspase-1 becomes activated which subsequently triggers interleukin-18 and interleukin-1β production. These interleukins further contribute to the development of the inflammatory cascade. In our study, we aim to examine and compare the expression levels of NLRP1, NLRP3, caspase-1, interleukin-18 and interleukin-1β by immunohistochemistry in lesional skin biopsies of 16 control group patients and 16 PLC, 12 stage 1 MF, and 12 non-stage 1 MF patients, thus we aimed to reveal inflammasome's role in pathogenesis of these two diseases. In paired comparisons of NLRP1 expression, a statistically significant difference was found between the control group vs. non-stage 1 MF group and between the control group vs the PLC group in terms of NLRP1. There was a statistically significant difference in IL- β expression between the control vs. non-stage 1 MF group, between the control vs. stage 1 MF group and between the control group and PLC group. In paired comparisons of caspase-1, a statistically significant difference was found between the control vs. PLC group, between the control vs. stage 1 MF group, and between the control vs non-stage 1 MF group in terms of caspase-1. In the pairwise comparisons of IL-18, a statistically significant difference was found between the control vs PLC group, between the control vs. stage 1 MF group and between the control vs. non-stage 1 MF group. Despite its limitations, in our study, it was revealed that inflammasome may play an important role in the pathogenesis of PLC and MF. Key words: inflammasome, mycosis fungoides, pityriasis lichenoides chronica Supporting Institution: Turkish Society of Dermatology