Common MS treatment linked to bowel disease risk
People with multiple sclerosis (MS) who are treated with rituximab have an increased risk of developing inflammatory bowel disease, particularly Crohn’s disease, although the absolute risk remains low. This is according to the first large population-based study in the field, led by researchers at Karolinska Institutet and published in JAMA Neurology.
Rituximab belongs to a group of drugs known as anti-CD20 therapies and is currently the most used disease-modifying treatment for MS in Sweden. As the use of anti-CD20 therapies has increased, cases of inflammatory bowel disease have been reported among patients receiving these treatments, raising concerns among neurologists. Until now, however, evidence from large studies has been lacking. The new study is the first population-based study to systematically investigate the association.
The researchers analysed nearly 14,000 treatment episodes among people with relapsing-remitting MS, using data from Swedish registers. They compared rituximab with three other highly effective MS treatments: natalizumab, dimethyl fumarate and fingolimod.
Inflammatory bowel disease was more common among people treated with rituximab than among those receiving any of the other three treatments, even after differences in follow-up time were taken into account. After adjusting for other differences between the groups, the researchers found that the risk was around ten times higher with rituximab than with the other MS treatments.
Few patients developed the disease
Despite the increased relative risk, the absolute risk remained low. Fewer than two per cent of patients in any of the treatment groups developed inflammatory bowel disease within ten years of starting treatment. The increase in risk corresponded to approximately one additional case for every 131 patients treated with rituximab for five years rather than with one of the other treatments. Most of the cases were Crohn’s disease.
“This is the first large study to quantify the risk of inflammatory bowel disease associated with anti-CD20 treatment for MS. The results show that this is a potential adverse effect that should be considered when choosing an MS treatment. At the same time, the increased risk needs to be weighed against the benefits for the individual patient. Anti-CD20 drugs are among the most effective treatments for preventing MS relapses,” says Peter Alping, researcher at the Department of Medicine, Solna, and last author of the study.
See the scientific article for information about funding and potential conflicts of interest.
Publication
“Risk of Inflammatory Bowel Disease Following Anti-CD20 Treatment in Multiple Sclerosis: A Population-Based Cohort Study”, Sandra Kallin, Anders Svenningsson, Ola Olén, Charlotte Hedin, Jan Lycke, Peter Alping, JAMA Neurology, online 22 October 2026, doi:10.1001/jamaneurol.2026.3439