Immunohistochemical Comparison of IL-36 and the IL-23/Th17 Axis of Generalized Pustular Psoriasis and Acute Generalized Exanthematous Pustulosis

Cutaneous pustular disorders include generalized pustular psoriasis (GPP) and acute generalized exanthematous pustulosis (AGEP). To identify differences between GPP and AGEP, here we immunohistochemically evaluated interleukin (IL)-36 and the IL-23/Th17 axis. 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. 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. Common pathomechanisms might exist in the development of GPP and AGEP based on these immunohistochemical results, but further studies are needed.