IFNB1 and inflammatory bowel disease: Inflammatory bowel disease (IBD): Severe colitis caused by Crohn’s disease was reported in a patient with MS treated with IFN-β.23 Aggravation and development of ulcerations was reported after treatment with IFN-β1a.24,25 A case of rapid-onset ulcerative colitis was reported one week after INF-β1a therapy.