In the last 20 years, anti-tumor necrosis factor (TNF)-α agents have been increasingly used for the treatment of patients affected by inflammatory bowel disease (IBD), such as Crohn’s disease (CD) and ulcerative colitis (UC), as well as rheumatologic and dermatological disorders such as rheumatoid arthritis (RA), juvenile idiopathic arthritis (JIA), ankylosing spondylitis (AS), psoriatic arthritis (PsA) and psoriasis. The gene discussed is TNF; the disease is Crohn disease.