Palmoplantar pustular psoriasis (PPPP) is characterized by activation of the IL-17A pathway.

BACKGROUND: Palmoplantar pustular psoriasis (PPPP) is a variant of psoriasis, which has significant negative impact on quality of life. The cellular and molecular inflammatory pathways involved in PPPP have not been well studied. OBJECTIVE: Study the expression of cytokines and chemokines involved in the IL-17/IL-23 axis in palmoplantar pustular psoriasis and other difficult to treat psoriasis areas (palms, scalp, elbows and lower legs). METHODS: Skin biopsies were performed on a total of 80 patients with PPPP, non-pustular palmoplantar psoriasis (NPPPP), or psoriasis located on elbows, knees and scalp as well as 10 healthy subjects. RT-PCR, immunohistochemistry and flow cytometry on cells extracted from skin biopsies were used to compare PPPP to other forms of psoriasis. RESULTS: There was a significant (p<0.05) increase in the expression of IL-1β, IL-6, LL-37, IL-19, IL-17A, CXCL1 and CXCL2 in PPPP as compared to NPPPP. However, there was no significant difference in expression of IL-23 in PPPP as compared to NPPPP and other forms of psoriasis. The proportion of IL-22but not IL-17Amast cells was higher in PPPP as compared to NPPPP (p<0.05). CONCLUSION: These results suggest that the IL-17A pathway may play a more important role in PPPP than in NPPPP.