New research findings indicate that IL-23 is one of the most important cytokines in the pathogenesis of psoriasis.2, 35 In 2016, Song et al. demonstrated, by immunohistochemistry, that IL-23 and IL-17 expressions were observed in the epidermis and perivascular dermal area in the psoriasis, suggesting that these interleukins play an important role in this disease.36 This evidence concerns the gene IL17A and psoriasis.