Breakdown of the genetics of Irritable Bowel Disease

Breakdown of the genetics of Irritable Bowel Disease
Irritable bowel disease (IBD) is a collection of autoimmune disorders that affect the digestive system. With no known cause or cure, IBD is a chronic, often life-long condition. Let’s dive into the science and genetics behind IBD to better understand what is known about IBD risk.
Written by Dave Gennert, PhD candidate
Orchid offers advanced genetic testing for couples who want their child to have the best shot of a healthy life. “Genetics for Humans” is where we unpack how genetics impacts our everyday lives and the latest tools to help you build a healthier family.

What is IBD, and how does it impact individuals?

When most people think of Irritable Bowel Disease, they tend to think of an upset digestive system triggered by food intolerances or stress. However IBD, unlike Irritable Bowel Syndrome (IBS), is an autoimmune disorder in which the body attacks its own healthy cells by mistake. This causes inflammation and can severely damage the bowel tissue if left untreated.

IBD is divided into two main subtypes: Crohn’s disease (CD) and ulcerative colitis (UC). Both subtypes have similar symptoms, including abdominal pain, persistent diarrhea, bloody stool, and fatigue. Serious complications can arise in cases of IBD that may require hospitalization and even surgery, which include bowel obstruction, fistulas, swelling of the large intestine called toxic megacolon, and an increased risk of colon cancer. So, IBD is often serious and can’t just “resolve on its own” with diet changes alone.

Treatments for IBD often include immune system modulators or suppressors, leading to increased susceptibility for certain infections and types of cancer. Surgery and bowel resection may be required in cases with severe inflammation or organ damage.

How common is Irritable Bowel Disease?

In 2015, 1.3% of American adults were reported to be diagnosed with IBD.A little over half of IBD patients have ulcerative colitis (53%), while a little under half (47%) have Crohn’s disease.Studies have shown that IBD has a higher rate of incidence in white Americans, especially those of Ashkenazi Jewish background, compared to other ethnic groups.

Does IBD run in families?

Yes, having family members with IBD predisposes someone to developing IBD themselves. A first-degree relative of a person with IBD has an estimated 5.2-22.5% risk of having IBD, while a child born to parents who both have IBD has a 1 in 3 risk of developing IBD by age 28.

Is there a single genetic cause for IBD?

For the vast majority of people diagnosed with IBD, no, a single gene or mutation is not the ultimate cause.

Rare cases of very-early-onset IBD (VEO-IBD, appearing before two years of age), however, are often associated with single mutations that disrupt important immunity-related genes.

However, most cases of IBD are due to a combination of genetic and environmental factors that affect the immune system, the tissues of the digestive tract, and the collection of microorganisms living in the gut, known as the microbiome.

Is there a genetic test for IBD?

Yes, there is now a way to measure your genetic predisposition for IBD. This is different from a diagnosis, however. Genetic screening can tell you if you are more or less likely to develop IBD than the average person based on your genetic background.

This is done by factoring in all the variants across the genome that we know increase the risk of IBD. Researchers so far have pinpointed 240 genetic markers in the genome with the highest effect for conferring risk for IBD. By comparing the DNA of thousands of people with IBD to thousands of healthy individuals, they have identified DNA sequences more likely to occur in people with the condition. Recent research found that 3.2% of the population is three times more likely to develop IBD based on screening for these genetic markers.

A person’s genetic background can also impact how much risk a particular risk marker contributes. For example, Ashkenazi Jewish individuals, who have an increased risk of IBD, have a different mix of common genetic risk markers than other ancestry groups.

As scientists learn more about the genetics underlying IBD, individual mutations that increase risk, decrease risk, or impact the effectiveness of certain therapies against IBD are continually being discovered. Other studies have found that combining genetic screening with established clinical risk factors for IBD, such as family history, smoking, and stool sample biomarkers, increases the predictive ability to assess overall risk for IBD.

With Orchid’s advanced genetic testing, you can get a sense of your genetic predisposition to IBD and remove some of the guesswork on what you can pass on to your future children.

What actions can I take based on the information from a genetic test for IBD?

If you or your future child has an elevated genetic risk for IBD, the risk of developing IBD at some point in life can be over three times higher than in the general population.

The useful thing about your results is that if you identify certain genetic vulnerabilities that can impact you or your future children, you can potentially do something about it and mitigate these risks. Ways you can act on your results include:

  • Offset genetic risks with healthy lifestyle choices.  Although the ultimate causes of IBD remain unknown, lifestyle factors contribute to IBD risk and severity of IBD symptoms. Stopping smoking, increasing physical activity and exercise, and eating a diet low in polyunsaturated fats and high in fiber have been associated with a lower risk of IBD.
  • Formulate a plan with your doctor.  Based on your genetic risk, your doctor may want to keep a closer eye on any potential IBD symptoms in order to catch the disease at an early stage. There are many tools available to test for IBD, including blood tests, imaging, and endoscopies, which can help diagnose IBD before serious complications arise.
  • Embryo screening to reduce your child’s potential genetic risks. Embryo screening allows you to assess each embryo’s genetic risk for IBD and other common conditions. This allows you to prioritize the transfer of embryos with the lowest genetic risk and thus reduce your future child’s genetic risks.

Key Takeaways

  • IBD is an autoimmune disease, where the immune system causes chronic inflammation along the digestive tract.
  • Genetics and lifestyle can predispose a person to developing IBD, while smoking cessation, physical activity, and diet can help reduce that risk.
  • Advanced genetic testing can now quantify the genetic component to IBD for you and your family.
Resources
Orchid offers advanced genetic testing for couples planning on building their family. We use advanced tools and smart, caring humans to help you give your future children the best shot of a healthy life. Conceive with greater confidence and peace of mind
2/22/2021
Genetics
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