Evidence for the involvement of eicosanoids in psoriasis is supported by mouse models of the disease—the leukotriene B4 (LTB4) receptor 1 and TxA2 receptor have critical roles in imiquimod-induced skin inflammation [24,25,26], and prostaglandin E2 (PGE2) acting at prostaglandin receptors EP2 and EP4 is important for Th17-dependent inflammation in interleukin 23 (IL-23)-induced psoriasis [27]. This evidence concerns the gene PTGER4 and psoriasis.