Crohn disease

[Raeanne Dimick]

Crohn disease is an inflammatory bowel disease where chronic inflammation typically involves the lower part of the small intestine, the large intestine, or both and may affect any part of the digestive tract.

Although the exact cause is unknown, an improperly functioning immune system may result in Crohn disease.
Typical symptoms include chronic diarrhea (which sometimes is bloody), crampy abdominal pain, fever, loss of appetite, and weight loss.
The diagnosis is based on a colonoscopy, video capsule endoscopy, and imaging tests such as barium x-rays, computed tomography, or magnetic resonance imaging.
There is no cure for Crohn disease.
Treatment is aimed at relieving symptoms and reducing inflammation, but some people require surgery.

(See also Overview of Inflammatory Bowel Disease (IBD).)
In the past few decades, Crohn disease has become more common worldwide. However, it is most common among people of Northern European and Anglo-Saxon descent. It occurs about equally in both sexes, often runs in families, and seems to be more common among Ashkenazi Jews. Most people develop Crohn disease before age 30, usually between the ages of 14 and 24. A few people have their first attack between the ages of 50 and 70.
Most commonly, Crohn disease occurs in the last portion of the small intestine (ileum) and in the large intestine, but it can occur in any part of the digestive tract, from the mouth to the anus and even in the skin around the anus. Inflammation of the ileum is called ileitis. When Crohn disease affects the colon, it is called Crohn colitis. Crohn disease affects

The small intestine alone (35% of people)
The large intestine alone (20% of people)
Both the last portion of the small intestine and the large intestine (45% of people)

The rectum is usually not affected, unlike in ulcerative colitis, in which the rectum is always involved. However, infections and other complications around the anus are not unusual. The disease may affect some segments of the intestinal tract while leaving normal segments (called skip areas) between the affected areas. Where Crohn disease is active, the full thickness of the bowel is usually involved.
The cause of Crohn disease is not known for certain, but many researchers believe that a dysfunction of the immune system causes the intestine to overreact to an environmental, dietary, or infectious agent. Certain people may have a hereditary predisposition to this immune system dysfunction. Cigarette smoking seems to contribute to both the development and the periodic flare-ups (bouts or attacks) of Crohn disease. Oral contraceptives may increase the risk of Crohn disease.
For unclear reasons, people who have a higher socioeconomic status may have an increased risk of Crohn disease.
Several reports suggest that people who were breastfed may be protected from developing inflammatory bowel disease.