This gluten allergy, known
as celiac disease, is thought to be inherited to some extent, but the
current study is the largest to date to look at identical and non-identical
twins.
By comparing identical twins,
who are genetically the same, to non-identical twins, who share only
the same number of genes as most other siblings, researchers
can help determine how much of an ailment is genetic and how much is due
to a shared environment.
In the new study, the investigators
found that environmental factors have little or no effect on the digestive
disorder, which can cause diarrhea, weight loss, stomach bloating and
damage to the small intestine.
This study provides substantial
evidence for a very strong genetic component in celiac disease. They suggest
that several genes work collectively to cause the disorder. A single missing
or altered gene is probably not to blame.
The findings are based on blood
samples drawn from 47 identical and non-identical twin pairs, where at
least one twin had been diagnosed with celiac disease. Individuals were
tested for antibodies that are specific to the disease.
According to the results, 38%
of the twin pairs both had signs of celiac disease -- 75% of identical
twins and 11% of non-identical twins.
In other findings, females
who had an affected twin were 30% more likely than an unaffected male
twin to go on to develop the disease themselves.
A shared environment did not
affect the risk of developing the disease, the study found.
Although some genetic variations
are known to increase the risk of the disease, much searching has not
located a gene that exerts a major affect.
It is more likely that a series
of genetic characteristics which individually exert little effect but
which collectively characterize a large gluten intolerant tribe that is
spread throughout the gluten-consuming world.
Gut
April 2002;50:624-628
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