Crohn’s disease is a type of bowel disease that causes inflammation in the intestines. Researchers do not know exactly why Crohn’s disease develops in some people, but genetic factors seem to play a role.

Experts believe that a combination of genetic factors and environmental triggers leads to Crohn’s disease.

Crohn’s, which is a type of inflammatory bowel disease (IBD), causes ongoing inflammation and thickening of the lining of the intestines. It can affect any part of the intestinal tract.

This article explores the role of genetics in Crohn’s disease.

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It appears that Crohn’s disease can sometimes have a genetic link. Having a close relative with Crohn’s disease increases an individual’s chances of developing the condition.

For instance, about 20% of people with Crohn’s disease have a close relative, such as a parent, brother, or sister, with some type of IBD.

Family links

The risk of developing Crohn’s disease increases if both parents have IBD.

The National Human Genome Research Institute notes that if one parent has Crohn’s disease, a child has a 7–9% risk of developing the disease. However, if both parents have IBD, that risk increases to about 35%.

Additional studies indicate that in identical twins, if one twin has Crohn’s disease, the other twin has a 50% chance of having the condition.


Researchers are still investigating how genetics influences the development of Crohn’s disease. Various genes may increase a person’s likelihood of developing IBD. Studies have identified more than 200 genes that may have links to this condition.

Some of these genes are recessive, which means that they only affect people who inherit two copies. For example, it appears that mutations in NOD2 may account for about 7–10% of early onset Crohn’s disease.

Studies have also identified other specific genes that may play a role in the development of Crohn’s disease. These include ATG16L1, IRGM, and IL23R, which help make proteins that affect the immune system’s function.

Variations or mutations in these genes may alter how the intestinal cells respond to bacteria. The disruption can cause ongoing inflammation, potentially contributing to symptoms of Crohn’s disease.

Crohn’s disease occurs equally in females and males. Although it can develop at any age, the disease most commonly appears between the ages of 20 and 30 years.

In addition to genetics, other factors may contribute to Crohn’s or increase the chances of developing the disease.

Environmental association

Certain factors may trigger an abnormal response by the immune system, which leads to inflammation in the digestive tract.

Scientists suspect that these environmental triggers include smoking and pollutants, but more research is necessary to confirm this.

An overactive immune system

In a person with Crohn’s disease, the immune system may go into overdrive.

The immune system may mistake gut bacteria, which are harmless, as invaders and launch a response to destroy them. This response leads to inflammation and symptoms of Crohn’s disease.

Doctors may be able to determine whether someone is prone to Crohn’s disease by carrying out tests. Various tests are available.

Genetic testing

Genetic testing identifies whether a person carries a mutation in a gene that could cause Crohn’s disease.

However, if someone does have an inherited gene mutation, it does not necessarily mean that they will develop Crohn’s disease. The gene just increases their risk.

Prenatal testing

Prenatal testing involves testing the fetus for the presence of a mutation in the NOD2 gene, which increases the risk of Crohn’s disease.

Pregnant people who have the mutation of this gene or have a relative with the mutation may have the option of prenatal testing.

Doctors diagnose Crohn’s disease using a combination of tests and a physical exam.

The symptoms of Crohn’s disease can be similar to those of other forms of IBD. Therefore, the process of diagnosis may include ruling out other conditions.

A medical exam may include a review of signs and symptoms to check for a pattern of flare-ups and assess the frequency and severity of symptoms.

Doctors may also perform a physical exam to check for stomach pain and other signs that may rule out other conditions.

Possible tests to diagnose Crohn’s disease may include:

  • Blood tests: Blood tests can identify low red blood cell levels and possible anemia. Blood work also checks the sedimentation rate, which indicates the presence of inflammation in the body.
  • Stool sample: A stool sample helps doctors detect infection and bleeding in the intestines.
  • Upper GI series: An upper GI series involves X-rays of the small bowel to check for abnormalities.
  • Colonoscopy: During a colonoscopy, a doctor will insert a scope with an attached camera through the anus into the colon to provide a visual exam of the intestines. It helps the doctor identify bleeding or inflammation of the intestines.
  • Enterography: A doctor may use a CT or MRI scan to check for signs of the disease in the small bowel.

The symptoms of Crohn’s disease may vary in intensity and frequency. It is common for symptoms to come and go.

Typical symptoms of Crohn’s disease include:

Some people develop additional symptoms outside of the intestinal tract. Symptoms in other parts of the body can include:

Learn about the staging of Crohn’s disease here.

There is currently no cure for Crohn’s disease, but the condition is manageable.

The frequency and severity of symptoms may vary among individuals. However, treatments and lifestyle changes may help minimize them.

Some people also experience remission from the disease and do not have symptoms for years.

Learn about treatment options for Crohn’s disease here.

Genetics may play a role in the development of Crohn’s disease. Researchers have identified several genes that may lead to changes in the immune system and make someone susceptible to the condition.

However, genetics alone is not the only cause of the disease. It is likely that a combination of genetics and environmental factors leads to Crohn’s disease.