A study has recently shown why anti-TNF drugs, which help treat autoimmune conditions such as rheumatoid arthritis, exacerbate multiple sclerosis. Researchers found that a variant of the TNFRSF1A gene previously associated with increased risk of developing multiple sclerosis encodes a shorter form of the TNFRSF1A protein. This shortened protein blocks TNF signalling, thereby having the same effect as the anti-TNF drugs. For more on this story, see www.bbc.co.uk/news/health-18738785.