Small intestine in Crohn's disease. Endoscopic view of ulceration (white) and inflammation affecting the neoterminal ileum (small intestine) of a patient with Crohn's disease. Crohn's disease is an autoimmune disease causing chronic inflammation of the gastrointestinal tract, primarily affecting the small intestine. It can cause ulceration, pain, discomfort, malabsorption leading to malnutrition, and bleeding leading to anaemia. Treatment is through anti-inflammatory steroids and anti-TNF biologic drugs. There is no cure.