Crohn Disease
What is Crohn disease?
Crohn disease is a complex, chronic disorder that primarily affects the digestive system. This condition typically involves abnormal inflammation of the intestinal walls, particularly in the lower part of the small intestine (the ileum) and portions of the large intestine (the colon). Inflammation can occur in any part of the digestive system, however. The inflamed tissues become thick and swollen, and the inner surface of the intestine may develop open sores called ulcers.
Crohn disease most commonly appears in a person's late teens or twenties, although the disease can appear at any age. Signs and symptoms tend to flare up (recur) multiple times throughout life. The most common features of this condition are persistent diarrhoea, abdominal pain and cramping, loss of appetite, weight loss, and fever. Some people with Crohn disease have chronic bleeding from inflamed tissues in the intestine; over time, this bleeding can lead to a low number of red blood cells (anaemia). In some cases, Crohn disease can also cause medical problems affecting the joints, eyes, or skin.
Intestinal blockage is a common complication of Crohn disease. Blockages are caused by swelling or a buildup of scar tissue in the intestinal walls. Some affected individuals also develop fistulae, which are abnormal connections between the intestine and other tissues. Fistulae occur when ulcers break through the intestinal wall to form passages between loops of the intestine or between the intestine and nearby structures (such as the bladder, vagina, or skin).
Crohn disease is one common form of inflammatory bowel disease (IBD). Another type of IBD, ulcerative colitis, also causes chronic inflammation of the intestinal lining. Unlike Crohn disease, which can affect any part of the digestive system, ulcerative colitis typically causes inflammation only in the colon. In addition, the two disorders involve different patterns of inflammation.
How common is Crohn disease?
Crohn disease is most common in western Europe and North America, where it has an estimated incidence of about 7 in 100,000 people. About one million Americans are currently affected by this disorder. Crohn disease occurs more often in Caucasians (whites) and people of eastern and central European (Ashkenazi) Jewish descent than among people of other ethnic backgrounds.
What genes are related to Crohn disease?
Variations of the CARD15 gene increase the risk of developing Crohn disease.
A variety of genetic and environmental factors likely play a role in causing Crohn disease. Although researchers are studying risk factors that may contribute to this complex disorder, most of these factors remain unknown. Cigarette smoking is thought to increase the risk of developing this disease, and it may also play a role in periodic flare-ups of signs and symptoms.
Studies suggest that Crohn disease may result from a combination of certain gene variations, changes in the immune system, and the presence of bacteria in the digestive tract. Most of the genetic changes have not been identified, although variations in one gene, CARD15, have been strongly associated with an increased risk of developing Crohn disease in the ileum. This increased risk has been found only in Caucasian populations. The CARD15 gene provides instructions for making a protein that helps protect the intestinal lining from bacterial infection. Changes in this gene prevent cells in the intestine from responding normally to bacteria, which may lead to the chronic inflammation characteristic of Crohn disease.
Several other genes are under study as possible risk factors for Crohn disease. Additional research is needed to determine what role these genes play in the development of this disorder.
How do people inherit Crohn disease?
The inheritance pattern of Crohn disease is unclear because many genetic and environmental factors are likely to be involved. This condition tends to cluster in families, however, and having an affected family member is a significant risk factor for the disease.
What other names do people use for Crohn disease?
- Colitis, Granulomatous
- Crohn's Disease
- Crohn's enteritis
- Enteritis, Granulomatous
- Enteritis, Regional
- Ileitis
- Ileocolitis
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