Crohn's disease, also known as Crohn syndrome and regional enteritis, is a type of inflammatory bowel disease that may affect any part of the gastrointestinal tract from mouth to anus, causing a wide variety of symptoms. It primarily causes abdominal pain, diarrhea (which may be bloody if inflammation is severe), vomiting, or weight loss, but may also cause complications outside the gastrointestinal tract such as anemia, skin rashes, arthritis, inflammation of the eye, tiredness, and lack of concentration. Crohn's disease is caused by interactions between environmental, immunological and bacterial factors in genetically susceptible individuals. This results in a chronic inflammatory disorder, in which the body's immune system attacks the gastrointestinal tract possibly directed at microbial antigens. While Crohn's is an immune related disease, it does not appear to be an autoimmune disease (in that the immune system is not being triggered by the body itself). The exact underlying immune problem is not clear; however it may be an immune deficiency state.
There is a genetic association with Crohn's disease, primarily with variations of the NOD2 gene and its protein, which senses bacterial cell walls. Siblings of affected individuals are at higher risk. Males and females are equally affected. Smokers are two times more likely to develop Crohn's disease than nonsmokers. Crohn's disease affects between 400,000 and 600,000 people in North America. Prevalence estimates for Northern Europe have ranged from 27–48 per 100,000. Crohn's disease tends to present initially in the teens and twenties, with another peak incidence in the fifties to seventies, although the disease can occur at any age. There is no known pharmaceutical or surgical cure for Crohn's disease. Treatment options are restricted to controlling symptoms, maintaining remission, and preventing relapse. The disease was named after gastroenterologist Burrill Bernard Crohn, who, in 1932, together with two other colleagues at Mount Sinai Hospital in New York, described a series of patients with inflammation of the terminal ileum, the area most commonly affected by the illness.