IL23A and psoriasis: Psoriatic plaques harbor higher levels of IL-23p19 and IL-12/23p40 than those of IL-12p35 [1, 27]; polymorphisms in IL12/23p40 and IL23R genes are associated with increased risk of developing psoriasis, and injection of recombinant IL-23 into healthy skin results in inflammatory changes with histologic features of psoriasis [5, 30].