A case study highlighted the rare occurrence of immune colitis associated with rituximab (RTX) therapy in a patient with relapsing multiple sclerosis (RMS), prompting the need for increased awareness and monitoring of this potential adverse effect in clinical practice.

B-cell–depleting therapies are commonly used to treat autoimmune conditions, including MS. Although the full safety profile of anti-CD20 therapies in MS is unknown, rare cases of secondary autoimmune conditions like colitis have been reported with RTX and ocrelizumab. The risk factors for these rare conditions are not well understood. This study describes a case of RTX-associated immune colitis in a patient with relapsing MS and reviews similar cases in the literature.

A 54-year-old woman with a 26-year history of RMS received her last routine RTX infusion in May 2023 after being managed on RTX 1000 mg every 6 months for 6.5 years. Following the infusion, she developed persistent abdominal pain and non-bloody diarrhea, prompting evaluation by a gastroenterologist. Stool studies and a celiac panel were negative, but a colonoscopy with biopsies revealed evidence of lymphocytic colitis. Treatment with steroid taper and antidiarrheals led to partial resolution of symptoms. Due to ongoing diarrhea and concern that the colitis was drug-related, discussion was ongoing to transition to another disease-modifying therapy. 

A review of the literature revealed similar adverse effects of RTX therapy in patients with autoimmune conditions, often showing symptoms within weeks to months of treatment and evidence of inflammation in the colon. Some cases may require steroid therapy, but discontinuation of RTX is not always necessary if symptoms improve. Additionally, ocrelizumab use may also be linked to this rare adverse effect.

“Immune colitis is a possible adverse effect of rituximab and other B-cell–depleting therapies,” said researchers. “We report a case of persistent diarrhea in a patient treated with RTX for > 6 years who was found to have lymphocytic colitis consistent with RTX-associated immune colitis. Clinicians should be aware of and monitor for this rare adverse effect and have a low threshold for referring to gastroenterology.” 

Reference 
Elfasi A, Newsome S D. Rituximab-associated immune colitis in multiple sclerosis: case report and literature review; CMSC 2024; May 29-June 1, 2024; Nashville, TN; Abstract CS01.