TNF-α inhibitors (TNFis) have revolutionized the treatment of certain chronic immune-mediated diseases, being widely and successfully used in rheumatic inflammatory diseases, and have also proved their efficacy in the treatment of inflammatory bowel disease (IBD). However, among the side effects of these agents are the so-called paradoxical effects. They can be defined as the appearance or exacerbation of a pathological condition that usually responds to this class of drug while treating a patient for another condition. A wide range of paradoxical effects have been reported including dermatological, intestinal and ophthalmic conditions. The causal mechanism of occurrence may implicate an imbalance of cytokines, but is still not fully understood, and remains a matter of debate. These paradoxical reactions often show improvement on discontinuation of the medication or on switching to another TNFi, but in some cases it is a class effect that could lead to the withdrawal of all anti-TNF agents. Close monitoring of patients treated with TNFis is necessary in order to detect paradoxical reactions. In this study we focus on reviewing IBD occurrence as a paradoxical effect of TNFi therapy in patients with rheumatological diseases (rheumatoid arthritis, psoriatic arthritis, ankylosing spondylitis, and juvenile idiopathic arthritis).
