Inflammatory bowel disease (IBD)is an autoimmune disease consisting of Crohn's disease and ulcerative colitis. Unlike the poorly understood but more common condition known as irritable bowel syndrome (IBS), IBD is frequently associated with symptoms occurring outside the bowel. These can include inflammation of the eyes, mouth ulcers, joint pain or swelling, and other inflammatory-related conditions.
Researchers have now shown that people with IBD have a higher than normal risk for developing multiple sclerosis and other autoimmune disorders. The full article is here (click on View print version (PDF)).

This risk is independent of treatment, but note that the medications used for IBD treatment, which block TNF-alpha (like Remicade and Humira), are also suspected of causing MS.Gastroenterology Online