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Ulcerative Colitis

What Causes Ulcerative Colitis?

Last modified: 
26/04/2012 - 09:37

Contributing Author: Guy Slowik FRCS

To date, there is no known cause for ulcerative colitis. Therefore, ulcerative colitis is said to be an idiopathic disease, meaning that it develops without an apparent or known cause.

Ulcerative colitis appears to be a disease primarily of those living in Western, industrialized societies. Whether this is because of some kind of condition of the environment in which people live, or their diet, is not known.

Two factors seem to play a role, however:

Weakened Immune Response

Between one billion and one trillion normal intestinal bacteria (enteric microflora) exist in every gram of intestinal content.

  • In the healthy intestine, invading bacteria are recognized as foreign (called antigens) and are attacked by the immune system.
  • But those bacteria that normally live there are left alone; the intestine is "tolerant" of such bacteria.

Immunologic evidence suggests that in the intestines of those with ulcerative colitis, some of this tolerance is lost. The TH1 cells, responsible for turning on the immunologic reaction against invading organisms, do their job; but the TH2 cells, responsible for turning the immunologic response off, fail to do their job. This causes an inappropriate inflammatory response.

Some evidence also points to flare-ups of ulcerative colitis or Crohn's disease as being an exaggerated response to seasonal allergies, upper-respiratory infections, or other transient illnesses.

Nice To Know:

One group of researchers has suggested that maybe the eradication of a group of parasites called helminthes (worms that live in the intestinal tract) through modern sanitation might have led to a state where the immune system does not have anything to practice on, and so attacks the body's own organs.

These researchers fed a group of six individuals suffering from flare-ups of Crohn's disease a formula made up of helminthes that breed in pig intestines. Five people went into remission and one improved fairly significantly. Since these helminthes do not breed in the human gut, it was easy for the researchers to check stool samples to see when the helminthes had all been passed from the test subjects' guts. After the worms were all gone, all of the subjects experienced a recurrence of their flare-ups.

The researchers hope to study groups of individuals who suffer from autoimmune conditions such as rheumatoid arthritis and lupus to see if a similar improvement in condition occurs with the helminthes treatment.

Is Ulcerative Colitis Inherited?

There is some evidence that ulcerative colitis has a genetic component.

Between 85 percent and 90 percent of people with ulcerative colitis have no relative with either ulcerative colitis or Crohn's disease. But the 10 percent to 15 percent of people who have relatives with ulcerative colitis or Crohn's means that the risk is statistically higher in individuals who have a family member with inflammatory bowel disease.

Other evidence points to a genetic basis: Populations that bred closely within their communities for many generations, such as Eastern European Jews, have a higher incidence of inflammatory bowel disease than other groups.

Nice To Know:

Q. If both parents have ulcerative colitis, what are the chances that their children will have ulcerative colitis?

A. Ulcerative colitis is not a strictly genetic disease. To date, scientists have found no specific gene that miscodes and causes ulcerative colitis. The chances of a child having ulcerative colitis if his or her parents do is only slightly greater than the chances of any child having ulcerative colitis.

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Ulcerative Colitis

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From Andrew Maynard - Chair of the University of Michigan Department of Environmental Health Sciences, with help from David Faulkner - 2013 Master of Public Health graduate.