IL19 and psoriasis: Therefore, combining the existing reports and our findings, here we present a conjecture: during the active inflammation of psoriasis, due to the decreased expression of IL-37, which is positively associated with melanogenesis, and the increased expression of IL-19, CXCL1, CXCL2, and CXCL13, which are negatively associated with melanogenesis, hypo-pigmentation in psoriatic lesions emerges.