Patients being treated with antiCD20 medications like ocrelizumab and rituximab may be at a higher risk of colitis and inflammatory bowel disease (IBD), according to a review article published in the journal Multiple Sclerosis and Related Disorders.

The review was published following the US Food and Drug Administration (FDA) issuing a warning about ocrelizumab use because of reports of colitis among patients using the drug.

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“Our study highlights the importance of clinicians being aware of this potential side effect,” the authors said. They added that patients who are treated with antiCD20 drugs should be closely monitored for gastrointestinal symptoms.

The authors presented 11 case reports of colitis among patients with multiple sclerosis (MS) being treated with antiCD20 drugs. Most of the patients were female and younger than age 50. Most had primary progressive MS (PPMS), and the average disease duration was 9 years. Only 1 patient had a known family history of IBD. 

The median duration of treatment with an antiCD20 drug was 18 months, and the mean number of cycles was 2.9. However, there was no significant association between the number of cycles and the development of colitis.

Symptoms of colitis, such as abdominal pain, diarrhea, and fever, occurred between 1 week and 18 months after the start of treatment with an antiCD20 drug. One case had systemic symptoms, which ultimately led to septic shock.

The authors also presented the cases of 2 patients with relapsing-remitting MS who were treated with ocrelizumab and who had possible IBD induced by the treatment and Crohn’s disease, respectively.

The authors and others proposed that immunological dysregulation due to B-cell depletion caused by antiCD20 drugs may be a possible mechanism for the development of colitis.

More research is needed “to determine the associated risk factors and to establish definitive guidelines for the clinical evaluation of MS patients on anti-CD20 medications,” the investigators wrote.

Ocrelizumab is the only therapy approved by the FDA to treat PPMS.


Tolaymat S, Sharma K, Kagzi Y, Sriwastava S. Anti-CD20 monoclonal antibody (mAb) therapy and colitis: a case series and review. Mult Scler Relat Disord. Published online May 15, 2023. doi:10.1016/j.msard.2023.104763