IL17A and psoriasis: This statement was supported by a meta-analysis by Liu et al. that found no significant correlation between IL-23 levels and psoriasis progression, and Nakajima et al. reported undetectable IL-17 and IL-23 levels in psoriasis and control groups, suggesting that these cytokines might be involved primarily in the early stages of psoriasis or may only show elevated levels in skin lesions [30, 31].