These pathways involve key cytokines and signal transducers, such as IL-23R, IL-12B, IL-21, IL-4, and IL-5, in psoriatic arthritis; IL-23R, IL-12B, IL-13, Rel, TYK2, and JAK2 in Crohn's disease (Ellinghaus et al., 2012; FitzGerald et al., 2015; Veale and Fearon, 2018). The gene discussed is IL23R; the disease is psoriatic arthritis.