IL23A and psoriasis: Meanwhile, several SNPs in the IL23A gene which code for the p19 subunit of IL-23 identified in European and Chinese populations have been associated with psoriasis susceptibility and immunopathogenesis via IL-23 signaling (Nair et al., 2009; Bowes et al., 2011; Li et al., 2016; Tsoi et al., 2017).