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