Introduction: Tumor necrosis factor (TNF) inhibitors (adalimumab, infliximab, etanercept, golimumab, and certolizumab pegol) have revolutionized the treatment of severe immune-mediated inflammatory diseases, including rheumatoid arthritis, Crohn’s disease, psoriatic arthritis, ankylosing spondylitis, and ulcerative colitis. The gene discussed is TNF; the disease is psoriatic arthritis.