TNF and rheumatoid arthritis: Biological agents, especially tumor necrosis factor inhibitors (TNFi), have revolutionized the therapeutic management of various chronic immune-mediated inflammatory diseases such as rheumatoid arthritis (RA), ankylosing spondylitis (AS), psoriatic arthritis (PA), juvenile idiopathic arthritis (JIA), inflammatory bowel disease (IBD), and psoriasis [1,2,3,4].