Immunohistochemical comparison of IL-36 and the IL-23/Th17 axis of generalized pustular psoriasis and acute generalized exanthematous pustulosis

Background: Cutaneous pustular disorders include generalized pustular psoriasis (GPP) and acute generalized exanthematous pustulosis (AGEP). Objective: To identify differences between GPP and AGEP, here we immunohistochemically evaluated interleukin (IL)-36 and the IL-23/Th17 axis. Methods: This retrospective comparative immunohistochemical study was completed using 11 biopsies of 11 cases of GPP and 11 biopsies of 11 cases of AGEP. Through staining with the anti-IL-36-alpha (IL-36α), anti-IL-36 receptor antagonist (IL-36Ra), anti-nuclear factor kappa-light-chain-enhancer of activated B cells (NF-κB), anti-IL-23, anti-IL-17, and anti-IL-8 antibodies, main expression location and intensity were visualized in the epidermis and dermis. Results: In both diseases, diffuse IL-36α expression was observed in the epidermis. IL-36Ra expression was observed in the dermal perivascular area as well as in the epidermis. NF-κB expression was observed in the epidermis and perivascular dermal area. Diffuse IL-23 and IL-17 expression was seen in the whole epidermis and the perivascular dermal area. IL-8 was expressed in the subcorneal pustules and parakeratotic area. Contrary to other cytokines, IL-23 expression in the epidermis of patients with GPP was more intense than only that in patients with AGEP. Conclusion: Common pathomechanisms might exist in the development of GPP and AGEP based on these immunohistochemical results, but further studies are needed.