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HLA-DQ9

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Updated April 07, 2012

Written or reviewed by a board-certified physician. See About.com's Medical Review Board.

Definition:

The gene HLA-DQ9 is not normally considered to be a gene that predisposes you to celiac disease. However, some recent research indicates that it might possibly play some role.

Most scientists believe that you need to carry particular genes in order to develop celiac disease. These so-called "celiac disease genes" include two specific HLA-DQ genes: HLA-DQ2 and HLA-DQ8.

You inherit one copy of an HLA-DQ gene from your mother and another from your father, which is why everyone carries two HLA-DQ genes. There are many different forms of the HLA-DQ gene, including the "celiac disease genes" HLA-DQ2 and HLA-DQ8, HLA-DQ7 and HLA-DQ1.

Almost everyone who is diagnosed with celiac disease carries HLA-DQ2 and/or HLA-DQ8. However, a very small percentage of celiacs don't carry either of those genes, and scientists are working to determine what other genes could be involved.

A study published in 2012 indicates that HLA-DQ9 might predispose you to celiac disease, even if you don't carry HLA-DQ2 or HLA-DQ8. That study, which looked at the activity of the genes at a molecular level, concluded that "DQ9 is a susceptibility factor for celiac disease," although it may not invoke as potent an effect as HLA-DQ8.

However, that research is very new and hasn't been backed yet by other studies, so it's not clear if scientists eventually will agree that HLA-DQ9 plays a role in celiac disease.

HLA-DQ9 may also play a role in gluten sensitivity. Much less is known about gluten sensitivity than about celiac disease, but there may be some common genetic issues involved.

Dr. Kenneth Fine, who directs the Enterolab gluten sensitivity testing laboratory, has conducted genetic research which he says indicates that HLA-DQ9 predisposes people to gluten sensitivity. However, his research hasn't been published and hasn't been accepted by mainstream physicians. Non-celiac gluten sensitivity research generally is a very new field, and there's not much known about the condition as of yet.

In the case of celiac disease, it's likely that there are many more genes involved in the development of the characteristic intestinal damage. Since gluten sensitivity research has really just begun, it's not even clear yet if that condition is caused or influenced strongly by your genes.

More on the genetics of celiac disease and gluten sensitivity:

Celiac Disease Genetic Testing
Gluten Sensitivity Genes
My close relative was diagnosed with celiac disease. Should I be tested?
I tested positive in my celiac gene test. Should I stop eating gluten now?

Sources:

Bodd M. et al. Evidence that HLA-DQ9 confers risk to celiac disease by presence of DQ9-restricted gluten-specific T cells. Human Immunology. 2012 Jan 31. [Epub ahead of print]

University of Maryland Center for Celiac Research fact sheet. Celiac Disease Frequently Asked Questions. Accessed March 20, 2012.

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