Causes of Ulcerative Colitis
What causes ulcerative colitis?
The causes of ulcerative colitis is not known. To date, there has been no convincing evidence that it is caused by infection or is contagious.
Many theories exist about what causes ulcerative colitis. People with ulcerative colitis have abnormalities of the immune system, but doctors do not know whether these abnormalities are a cause or a result of the disease. The body's immune system is believed to react abnormally to the bacteria in the digestive tract.
Ulcerative colitis is not caused by emotional distress or sensitivity to certain foods or food products, but these factors may trigger symptoms in some people. The stress of living with ulcerative colitis may also contribute to a worsening of symptoms.
Genetic factors
A genetic component to the aetiology of ulcerative colitis can be hypothesized based on the following:
- Aggregation of ulcerative colitis in families.
- Identical twin concordance rate of 10% and dizygotic twin concordance rate of 3%
- Ethnic differences in incidence
- Genetic markers and linkages
There are 12 regions of the genome which may be linked to ulcerative colitis. This includes chromosomes 16, 12, 6, 14, 5, 19, 1,and 3 in the order of their discovery. However, none of these loci has been consistently shown to be at fault, suggesting that the disorder arises from the combination of multiple genes. For example, chromosome band 1p36 is one such region thought to be linked to inflammatory bowel disease. Some of the putative regions encode transporter proteins such as OCTN1 and OCTN2. Other potential regions involve cell scaffolding proteins such as the MAGUK family. There are even human leukocyte antigen associations which may be at work. In fact, this linkage on chromosome 6 may be the most convincing and consistent of the genetic candidates.
Multiple autoimmune disorders have been recorded with the neurovisceral and cutaneous genetic porphyrias including ulcerative colitis, Crohn's disease, celiac disease, dermatitis herpetiformis, diabetes, systemic and discoid lupus, rheumatoid arthritis, ankylosing spondylitis, scleroderma, Sjogren's disease and scleritis. Physicians should be on high alert for porphyrias in families with autoimmune disorders and care must be taken with potential porphyrinogenic drugs, including sulfasalazine.
Environmental factors
Many hypotheses have been raised for environmental contributors to the pathogenesis of ulcerative colitis. They include the following:
- Diet: as the colon is exposed to many dietary substances which may encourage inflammation, dietary factors have been hypothesized to play a role in the pathogenesis of both ulcerative colitis and Crohn's disease. There have been few studies to investigate such an association, but one study showed no association of refined sugar on the prevalence of ulcerative colitis.
- Breastfeeding: There have been conflicting reports of the protection of breastfeeding in the development of inflammatory bowel disease. One Italian study showed a potential protective effect.
- Several scientific studies have posted that Accutane is a possible trigger of Crohn's Disease and Ulcerative colitis in some individuals. Three cases in the United States have gone to trial thus far, with all three resulting in multi-million dollar judgements against the makers of isotretinoin. There were an additional 425 cases pending as of.
Autoimmune disease
Some sources list ulcerative colitis as an autoimmune disease, a disease in which the immune system malfunctions, attacking some part of the body. In contrast to Crohn's disease, which can affect areas of the gastrointestinal tract outside of the colon, ulcerative colitis usually involves the rectum and is confined to the colon, with occasional involvement of the ileum. This so-called "backwash ileitis" can occur in 10–20% of patients with pancolitis and is believed to be of little clinical significance. Ulcerative colitis can also be associated with comorbidities that produce symptoms in many areas of the body outside the digestive system. Surgical removal of the large intestine often cures the disease.
Alternative theories
Levels of sulfate-reducing bacteria tend to be higher in persons with ulcerative colitis. This could mean that there are higher levels of hydrogen sulfide in the intestine. An alternative theory suggests that the symptoms of the disease may be caused by toxic effects of the hydrogen sulfide on the cells lining the intestine.
