About Genetic Risk & Celiac Disease

23andMe Celiac Disease Risk Markers

[This was a reply to an email question about genetic risk of celiac. I have so much to share here, but so little time for blogging, that I decided to grab this part, and hope to add more of my recent explorations in the future. Not TOO distant, I hope!]


Like so many people, I failed all the blood tests for celiac, despite having a boatload of symptoms. That was why I took the 23andMe test for celiac markers, with the results showing 4.07 times the normal risk of celiac. In the general population, risk is 0.24%; mine was 0.96%. There are currently 4 known genetic markers for celiac:

* HLA-DQA1 (SNP rs2187668)
* 4q27 (SNP rs6822844)
* 3p21 (SNP rs6441961)
* 3q28 (SNP rs9851967)

I have 3 of the 4, all except the last and least important one, which is what made for 0.96%. Now, ~1% that sounds awfully small, but the genetic risk combines with a variety of other risk factors.

“Estimates of the heritability of Celiac Disease vary. Risk factors other than the SNPs mentioned here include having European ancestry, family history of Celiac Disease, and a personal history of other autoimmune disorders. These disorders include Systemic Lupus Erythematosus, Type 1 Diabetes, Autoimmune Thyroid Disease, and Rheumatoid Arthritis.”

I have European ancestry, family history, and a family history (not personal history) of the autoimmune disorders listed as examples, with a personal history of autoimmune disorders not listed as examples. My diagnosis came from combining all of these:

* genetic risk factor PLUS
* family history PLUS
* ancestry PLUS
* other autoimmune disorders PLUS
* symptoms PLUS
* blinded trial

You see, the inclination of the docs was to read the symptoms as meaning a combination of a bunch of other possible conditions, which they’ve been attempting to treat for 10-20 years. Unsuccessfully. But we kept trying. Believe it or not, this made sense, specifically because, until we had all that information, the risk of the other conditions was higher than the risk of celiac, making it much more logical to explore those options.

They were reluctant to consider celiac, in part because it is a “fad” currently prone to self-diagnosis. Docs rightly tend to mistrust self-diagnoses of current fads, but then every now and then the fad was right! LOL! The other reason they were mistrusting this “self-diagnosis” was because I had atypical presentation of the symptoms. Most folk have primarily gut problems. I had mostly skin. Most folk with celiac related skin problems have those show up on limbs and back. Mine were worst on my face. Medically, it didn’t LOOK like celiac or dermatitis herpetiformis. They weren’t sure what it was, but it didn’t look like what it turned out to be. So you really can’t blame the docs.

But when you combined all these risk factors, you ended up with roughly 1/4 risk instead of 1/100. Big difference. Then the blinded trial tipped the balance. When you have someone with a 1/4 risk of celiac and symptoms and they pass a blinded trial, well, the reluctance to diagnose celiac faded.

EDIT:

I am adding a link to the article citation which was referenced in the test results. For those who want to explore more deeply.

van Heel DA, Franke L, Hunt KA, Gwilliam R, Zhernakova A, Inouye M, Wapenaar MC, Barnardo MC, Bethel G, Holmes GK, Feighery C, Jewell D, Kelleher D, Kumar P, Travis S, Walters JR, Sanders DS, Howdle P, Swift J, Playford RJ, McLaren WM, Mearin ML, Mulder CJ, McManus R, McGinnis R, Cardon LR, Deloukas P, Wijmenga C.
A genome-wide association study for celiac disease identifies risk variants in the region harboring IL2 and IL21.
Nat Genet. 2007 Jul;39(7):827-9. Epub 2007 Jun 10.
http://www.ncbi.nlm.nih.gov/pubmed?term=17558408

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