Inflammatory Bowel-Like Disease with Ileocolic and Perianal Involvement Induced by Ocrelizumab: A Case Report.

Introduction: Immune-mediated colitis (IMC) is a common immune-related adverse event associated with immune checkpoint inhibitors. Other classes of biological therapy, such as monoclonal antibody with anti-CD20 activity, have also been associated with drug-induced gastrointestinal injuries, although through different immunomechanisms. In the literature, there are some previously described cases reporting on enterocolitis induced by rituximab and ocrelizumab highlighting its potential severity. Consequently, recently, the FDA amended the Prescribing Information of ocrelizumab to include IMC in the Warnings and Precautions section. Case Presentation: We present the case of a patient with chronic diarrhea due to immune-mediated enterocolitis, markedly resembling Crohn's disease with ileocolic and perianal involvement induced by ocrelizumab. Endoscopically, this condition is indistinguishable from inflammatory bowel disease with significant overlap in histology. With discontinuation of ocrelizumab, the lesions and the symptoms disappeared. To our knowledge, this is the first case reporting perianal involvement. Conclusion: There are no clear recommendations on how to manage these patients. Clinicians must be aware of this entity and report on these unquestionably increasing conditions.