Crohn’s disease, also known as 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 at its worst), vomiting (can be continuous), or weight loss,[1][2][3] but may also cause complications outside the gastrointestinal tract such as skin rashes, arthritis, inflammation of the eye, tiredness, and lack of concentration.[1] Crohn’s disease is caused by interactions between environmental, immunological and bacterial factors in genetically susceptible individuals.[4][5][6] This results in a chronic inflammatory disorder, in which the body’s immune system attacks the gastrointestinal tract possibly directed at microbial antigens.[7][5] Crohn’s disease has traditionally been described as an autoimmune disease, but recent investigators have described it as a disease of immune deficiency. 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.[8] Males and females are equally affected. Smokers are two times more likely to develop Crohn’s disease than nonsmokers.[9] Crohn’s disease affects between 400,000 and 600,000 people in North America.[10] Prevalence estimates for Northern Europe have ranged from 27ñ48 per 100,000.[11] 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.[1][12] There is no known pharmaceutical or surgical cure for Crohn’s disease.[13] Treatment options are restricted to controlling symptoms, maintaining remission, and preventing relapse. The disease was named after American gastroenterologist Burrill Bernard Crohn, who, in 1932, together with two colleagues, described a series of patients with inflammation of the terminal ileum, the area most commonly affected by the illness.