Adverse effects of TNF inhibitors in SpA: are they different from RA?

Tumor necrosis factor (TNF) inhibitors were the first biologic drugs prescribed for the treatment of spondyloarthritis (SpA) and rheumatoid arthritis (RA). Although they provide significant improvement of signs and symptoms, TNF inhibitors need to be used frequently for a long period of time. The analysis of the follow-up of the largest national biologics registries has shown that the most important adverse effect of TNF inhibitors is infection, which is significantly higher than the non-biologic treatment group; reactivation of latent tuberculosis is three to four times more frequent in patients using monoclonal antibodies than soluble receptors. The only cancer site more frequent to be associated with TNF inhibitors in RA and SpA is the non-melanoma skin cancer. Paradoxical reactions do occur during anti-TNF treatment mainly in SpA, such as new manifestations or flares of acute uveitis, new onset of psoriasis, such as palmoplantar pustulosis, or new onset or flares of inflammatory bowel disease, which occurs especially during etanercept treatment.