Crohns genetic testing

[Rwolf]

Has anyone ever had genetic testing for crohns and if so are the results always right ?

 

[Scipio]

The term "genetic testing for Crohn's" could mean a lot of different things depending on which genes are tested for. There are a bunch of genes associated with increased risk of having Crohn's or increased risk of having severe, aggressive Crohn's if you have the disease in the first place. There is no simple Yes/No genetic testing for prediciting or diagnosing Crohn's. It's more like forecasting the weather. If the weatherman says there will be a 40% chance of rain tomorrow and tomorrow it starts to rain, was the weatherman right or wrong?

I have been tested for five different Crohn's-associated genes (SNPs): ATG16L1, ECM1, NKX2-3, STAT3, and NOD2. I tested Positive for increased risk of Crohn's by STAT3 and Negative by the other four tests, and I do in fact have Crohn's. So was the genetic testing right? It depends on your definition of "right."

It's really hard to say whether the testing was right because we are not dealing with with a yes or no question. We are dealing with probabilities. The more of these risk genes you test positive for (and there are more than just these five), the more likely you are to get Crohn's. But nothing is a sure thing. Testing all five negative does not mean that you absolutely can't get Crohn's, and testing all five positive does not ensure that you absolutely will get Crohn's.

 

[Rwolf]

Thank you so much for this information .

 

[JasonBourne]

Does anyone know if certain genetic markers guide treatment?

Soon after diagnosis, my GI said they would do a variety of genetic testing, but so far nothing for 9mo. A rheumatologist actually asked for routine blood work for me, and I believe 1 genetic test for AS. Is that all anyone really needs to know? I suspect if they had a higher genetic link to treatments they would do it but....

Although I’ve come a long way, still many things to learn. Let me know what you think. GI would like to start Infliximab any day (Remicade biosimilar), but timing now likely pushes this further out.

 

[kiny]

It's only useful for research, not for patients.

Thanks to looking at specific genes we have managed to further establish that crohn's disease is related to a primary immunodeficiency, which affects clearance of bacteria and fungi from the lamina propria.

But it's of no direct use to the patient. It's of zero use during diagnosis, because far more people with those genetic mutations don't have crohn's than those that do.

It's also of no use for an active patient, it changes nothing. All a doctor could say is that patients with certain genetic variants might have a worse or more gentle disease course, it would do nothing but scare a patient and it would be inaccurate most of the time.

 

[kiny]

If you're not caucasian, genetic testing is even more useless. It's mostly caucasians with crohn's disease who have those specific mutations. People from South-East Asia and China generally do not, in Japan few have them.

Why caucasians have those mutations and not other races is related to the past. Those mutations probably protect us from Yersinia pestis, responsible for the plague in Europe.

The plague wiped out half of Europe's population, and we suspect survival rates were much higher among those with those specific genetic mutations. So you end up with a variants slanted towards caucasians, variants that you don't see in other parts of the world where the plague didn't manifest itself to the same extent.

It is probably part of the reason why Crohn's disease is more prevalent in Western society. Even though incidence of crohn's disease is on the rise in Asia, prevalence is still much lower.

So...if the plague comes back...we'll all by standing and everyone else will be toast, comforting.

 

[JasonBourne]

It's also of no use for an active patient, it changes nothing. All a doctor could say is that patients with certain genetic variants might have a worse or more gentle disease course, it would do nothing but scare a patient and it would be inaccurate most of the time.

It may change how seriously some patients (me) giddy up and go with treatment, diet, stress reduction etc...

Why caucasians have those mutations and not other races is related to the past. Those mutations probably protect us from Yersinia pestis, responsible for the plague in Europe.
...
So...if the plague comes back...we'll all by standing and everyone else will be toast, comforting.

Ha... unless we’re all suppressing our immune systems....