Crohn disease, or regional enteritis, is one form of the severe chronic disorder called inflammatory bowel disease. It mainly affects the small intestine but can occur anywhere along the digestive tract. The inflammation may cause episodes of pain, diarrhea, rectal bleeding, fever, and weight loss and may lead to problems such as mouth sores, arthritis, and liver, skin, or eye damage. Bowel obstruction and other complications may require surgical intervention. The cause of this potentially fatal disorder remains unknown. Because the symptoms resemble those of other conditions, Crohn disease is sometimes hard to diagnose. Drug treatments include steroids and sulfasalazine. Both can have serious side effects. Researchers have found that the drug inflimiximab lessens symptoms such as bowel inflammation. In August 1998 the U.S. Food and Drug Administration approved the drug for use in patients with moderate or severe forms of Crohn disease.