Chronic inflammation of part of the small intestine or large intestine (strictly, of the ileum). A more serious type, regional ileitis (Crohn disease), involves both small and large intestines. Ileitis symptoms include chronic or intermittent, sometimes bloody, diarrhea and abdominal cramps. Fever, weight loss, and anemia may occur. Crohn disease may involve progressive deterioration. Obstructions or abnormal connections between loops of intestine may develop. Simple ileitis has short-term causes, and many patients recover completely. In Crohn disease, which may result from an autoimmune defect, remissions and relapses continue for years, causing the intestine's wall to thicken, its channel to narrow, and its lining to ulcerate. X-ray films or colonoscopy showing these features are diagnostic. Drug treatment may help, but there is no known cure, and the disease often requires removal of part of the intestine.