Celiac Genes: How to Check Your Raw Data

Key takeaways:
~ Celiac disease is an autoimmune disorder in which gluten causes damage to the small intestines.
~ Celiac is only possible in people with specific HLA genotypes.
~ You can use your genetic raw data (23andMe, AncestryDNA, etc) to find out if you have the HLA type that makes you susceptible to celiac.

What is celiac disease?

Celiac disease (spelled coeliac in Britain) is an autoimmune disorder in which gluten, a protein found in wheat and other grains, leads to your body attacking its own cells.

Inside the small intestines, there are little projections called villi. In celiac disease, the body attacks those cells, causing the villi to shorten and not absorb nutrients very well.

Symptoms of celiac disease:

Symptoms of celiac disease can vary from person to person, but some common ones include: [ref]

• Gastrointestinal issues
• Tiredness or fatigue
• Nutrient deficiencies even when eating a good diet
• Anemia or iron deficiency
• Reduced bone density and early osteoporosis
• Canker sores
• Dermatitis herpetiformis (itchy skin rash)
• In children, poor growth and short stature

It’s also worth noting that not everyone with celiac disease will have all of these symptoms.

Is celiac disease hereditary?

Genetic diseases that are hereditary are caused by inheriting a genetic variant or mutation from your parents.

While there isn’t just one specific genetic variant that causes everyone who carries it to get celiac disease, it is hereditary and based on genetic variants.

It’s important to understand that not everyone who has these HLA types will develop celiac disease. In fact, almost 25% of the population has HLA-DQ2.5, and that percentage grows to ~30% when adding in HLA-DQ8 alleles.[ref]

With only ~1% of the population having celiac disease, you can see that just having the HLA type doesn’t mean that you will get celiac disease.

Thus, looking at your genetic variants can help you rule out celiac disease, but it cannot tell you if you have it.

What is an HLA serotype?

Serotypes, discovered in 1933 by Rebecca Lancefield, are variations within species (bacteria and viruses) or variations among immune cells in people. The typing is based on their cell surface antigens. In humans, the human leukocyte antigen (HLA) determines the serotype. HLA serotypes can be used in determining transplant matches.

One HLA type is HLA-DQ, which is a protein found on antigen-presenting cells. DQ is involved in the immune system by stimulating T-cells, which then signal B-cells to produce antibodies.

HLA-DQ recognizes foreign antigens from pathogens, but it also recognizes common self-antigens. This is where the problem begins when the HLA-DQ loses its tolerance to self-proteins, triggering autoimmune diseases such as celiac, lupus, and type 1 diabetes.

Diagnosing Celiac Disease:

There are blood tests that can show whether you carry antibodies against gluten. The test is not 100% accurate, and some people may have false-negative results (e.g., a blood test shows that you don’t have celiac when you do).

Genetics can help you rule out celiac disease. If you don’t carry the HLA type (below) and also have a negative antibody test, then celiac is highly unlikely.

The ‘gold standard’ is an intestinal biopsy, where a gastroenterologist takes a small snip out of your intestines to see if there is damage to the villi.

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