Interleukin (IL)-23 is a member of the IL-12 cytokine family and is implicated in a cluster of immune-mediated inflammatory diseases (IMIDs) that includes psoriasis (PsO), psoriatic arthritis (PsA), and inflammatory bowel disease (IBD; namely Crohn’s disease [CD] and ulcerative colitis [UC]) (1–8). The gene discussed is IL23A; the disease is psoriatic arthritis.