Crohn's disease is one of two chronic inflammatory bowel diseases (IBD) affecting the digestive system, the other being ulcerative colitis. These two disorders of the gastrointestinal (GI) tract have similar signs and symptoms, including diarrhea, abdominal pain and cramping, blood in the stool, and weight loss with poor appetite. According to the Crohn's and Colitis Foundation of America (CCFA), Crohn's can affect any part of the GI tract between the mouth and the anus but is usually found in an area of the small intestine called the ileum. For this reason, it is sometimes called ileitis. The inflammation involves of all the layers of intestine, but may be intermittent, with perfectly healthy tissue alternating with diseased spots.
Although the exact cause of Crohn's isn't known, research is focusing on the immune system, genetics and environmental factors.
Immune System Dysfunction
The body's immune system reacts to protect us against harmful organisms. However, in some instances, it makes a mistake. According to the National Institute of Diabetes and Digestive and Kidney Diseases, in Crohn's disease, it may be that the body thinks bacteria, foods and other substances are foreign substances. The result is that the immune system gears up to eliminate the offending organisms, causing a buildup of white blood cells in the lining of the GI tract. As these cells accumulate, chronic inflammation ensues, and ulcers eventually occur in the intestines. Studies are ongoing as of 2010, but researchers are not sure if the immune system dysfunction is a cause of Crohn's or a consequence of some other factor that underlies the disease.
Heredity
As the American Academy of Family Physicians points out, you can't catch Crohn's, but if you have a family member with the disease, you're more likely to also get it. This is why researchers are looking into genetics as a cause of Crohn's. According to the Mayo Clinic, people with Crohn's frequently have mutations in the NOD2 gene. In addition, those who have Crohn's and this mutation are also more likely to require surgery to control the disease. The CCFA points out that genetics alone aren't likely to be the cause of Crohn's, as the inflammation appears to result from the combination of the immune system, genetics and environmental factors. Genetics may, however, influence the body's ability to know when to stop the immune reaction, an avenue scientists are exploring in Crohn's research.
Environment
One area of research into the cause of Crohn's is the interaction of environmental factors with the immune system and a person's genetic makeup. According to the Crohn's and Colitis Foundation, these researchers believe that an agent such as a virus or bacterium may either trigger the immune system dysfunction or cause an injury to the lining of the intestine, which would then lead to or speed up the disease.
Risk Factors
While not a cause of a disease, risk factors help scientists identify areas of research, and they help doctors hone in on a diagnosis. The Mayo Clinic lists a number of risk factors for Crohn's including: age--onset occurs most frequently in young adults; ethnicity--it is more common among whites and Ashkenazi Jews, and less commonly found in African-Americans, Hispanics and Asians; cigarette smoking; where you live--this is a disease of developed nations; Isotretinoin (Accutane) use--more common among those who use this powerful acne medicine but cause and effect hasn't been proved; NSAID use--not a cause of Crohn's but can mimic or worsen the symptoms.
While diet and stress were long thought to be causes of Crohn's, the CCFA says there is no evidence to support this, though both can worsen symptoms.
