The invention of biological agents has greatly improved the treatment outcomes of psoriasis, including inhibitors of tumor necrosis factor (TNF)-α, interleukin (IL)-17, and IL-12/23 (Papp et al., 2008; Saurat et al., 2008; Barker et al., 2011; Paul et al., 2015; Gordon et al., 2016). The gene discussed is IL17A; the disease is psoriasis.