Crohn’s disease is an inflammatory bowel disease, the general name for diseases that cause swelling in the intestines. Because the symptoms of Crohn’s disease are similar to other intestinal disorders, such as irritable bowel syndrome and ulcerative colitis, it can be difficult to diagnose.

Crohn’s disease affects men and women equally and seems to run in some families. About 20 percent of people with Crohn’s disease have a blood relative with some form of inflammatory bowel disease, most often a brother or sister and sometimes a parent or child. Crohn’s disease can occur in people of all age groups, but it is more often diagnosed in people between the ages of 20 and 30. People of Jewish heritage have an increased risk of developing Crohn’s disease, and African Americans are at decreased risk for developing Crohn’s disease.

What causes Crohn’s disease?

Several theories exist about what causes Crohn’s disease, but none have been proven. The human immune system is made from cells and different proteins that protect people from infection. The most popular theory is that the body’s immune system reacts abnormally in people with Crohn’s disease, mistaking bacteria, foods, and other substances for being foreign. The immune system’s response is to attack these “invaders.” During this process, white blood cells accumulate in the lining of the intestines, producing chronic inflammation, which leads to ulcerations and bowel injury.
Scientists do not know if the abnormality in the functioning of the immune system in people with Crohn’s disease is a cause, or a result, of the disease. Research shows that the inflammation seen in the GI tract of people with Crohn’s disease involves several factors: the genes the patient has inherited, the immune system itself, and the environment. Foreign substances, also referred to as antigens, are found in the environment. One possible cause for inflammation may be the body’s reaction to these antigens, or that the antigens themselves are the cause for the inflammation. Scientists have found that high levels of a protein produced by the immune system, called tumor necrosis factor (TNF), are present in people with Crohn’s disease.

What are the symptoms of Crohn's disease?

Common symptoms of Crohn's disease include abdominal pain, diarrhea and weight loss. Less common symptoms include poor appetite, fever, night sweats, rectal pain, and rectal bleeding. The symptoms of Crohn's disease are dependent on the location, the extent, and the severity of the inflammation. The different subtypes of Crohn's disease and their symptoms are:

  1. Crohn's colitis is inflammation that is confined to the colon. Abdominal pain and bloody diarrhea are the common symptoms. Anal fistulae and peri-rectal abscesses also can occur.
  2. Crohn's enteritis refers to inflammation confined to the small intestine (the first part, called the jejunum or the second part, called the ileum). Involvement of the ileum alone is referred to as Crohn's ileitis. Abdominal pain and diarrhea are the common symptoms. Obstruction of the small intestine also can occur.
  3. Crohn's terminal ileitis is inflammation that affects only the very end of the small intestine (terminal ileum), the part of the small intestine closest to the colon. Abdominal pain and diarrhea are the common symptoms. Small intestinal obstruction also can occur.
  4. Crohn's entero-colitis and ileo-colitis are terms to describe inflammation that involve both the small intestine and the colon. Bloody diarrhea and abdominal pain are the common symptoms. Small intestinal obstruction also can occur.