Part 2: What is ulcerative colitis?

Ulcerative colitis1 is an intestinal inflammatory disease that affects the colonic mucosa (large intestine). This mucosa works as a barrier against harmful substances. It also helps secreting and transporting nutrients, water and minerals; and lubricating the inner part of the intestine in order to facilitate defecation. Its inflammation is produced because the immune system generates an inappropriate inflammatory response against the organism itself. The origin of this failure in the intestinal immune system’s responses is not fully known.

When the mucosa gets inflamed, little wounds (ulcers) appear in the inner lining of the colon. This chronic inflammation starts in the rectum and spreads out to other sections of the colon (ascending, transverse and descending). That means that the affectation may have a variable extension.

The most common symptoms of the ulcerative colitis are liquid defecations with mucus and/or blood, stomach ache, straining to defecate, fever, weight loss and fatigue. Besides, other organs like skin, eyes, bones, etc. may be affected. Most people suffering from ulcerative colitis experience from mild to moderate symptoms. There will be periods of activity when the symptoms occur (called flares). However, there are also periods of normality when the disease seems to disappear (called remission phases). Some people may experience long remission phases.

Risk factors As well as Crohn’s disease, UC is a modern age disorder. In fact, the frequency has increased in developed countries since the mid-twentieth century. This disease affects males and females approximately in equal proportions.
The risk factors may be:

  • Age. Even though it may appear at any age, it generally occurs before the age of 30. Nevertheless, there are also cases in which the disease has been diagnosed after the age of 60.
  • Race or ethnic origin. Although white people have a higher risk of experiencing the disease, any race can have it. If you have Ashkenazi Jewish ancestry, the risk is higher.
  • Family history. It is frequent to find UC cases within the members of the same family. Between 8 and 14% of the patients with ulcerative colitis have a family history of inflammatory bowel disease. Therefore, the risk increases when you have a close relative (parent, sibling or son/daughter) who suffers from this disease.


The cause of the ulcerative colitis and other unknown issues for the science Even though science has made great efforts to find out the cause of ulcerative colitis, it is still unknown. Science still wonders what the specific cause of the inappropriate inflammatory response of the immune system is. According to GETECCU2, current researches state that the disease may appear as a result of a complex interaction of several factors.

One of those factors is a person’s genetic predisposition (susceptibility) to suffer from the disease. However, there are other factors that also seem to be the key in the appearance of the UC like the exposition to environmental factors, the intestinal commensal microflora and the possible involvement of infectious agents. It is believed that the genetic alterations affect the ability of the immune system to tolerate the commensal bacteria and the intensity of the inflammatory response against those bacteria.

Nonetheless, the genetic origin is not completely clear yet. In conjunction with this issue, there exist questions about the pathogenesis of ulcerative colitis that still pose a challenge to science. Why is the inflammation restricted to the mucus layer? Are the epithelial cells of the colon the specific aim of an immune response? How does the luminal microbiota affect the inflammatory response?


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