Definition & Facts for Crohn’s Disease

What is Crohn’s disease?

Crohn’s disease is a chronic disease in which abnormal reactions of the immune system cause inflammation in your digestive tract. Most commonly, Crohn’s disease affects your small intestine and the beginning of your large intestine. However, the disease may affect any part of your digestive tract, from your mouth to your anus.

Crohn’s disease is an inflammatory bowel disease (IBD). Ulcerative colitis and microscopic colitis are other common types of IBD.

Crohn’s disease most often begins slowly and may get worse over time. Symptoms can range from mild to severe. When people have symptoms, it’s called a flare. In between flares, most people have periods of remission—times when symptoms disappear. Periods of remission can last for weeks or years. The goal of treatment is to keep people in remission long term.

How common is Crohn’s disease?

Researchers estimate that 1 million people in the United States have Crohn’s disease.1 Studies show that Crohn’s disease has become more common in the United States and other parts of the world. Experts do not know the reason for this increase.

Who is more likely to develop Crohn’s disease?

Crohn’s disease can develop in people of any age or race, but is more likely to develop in people who

  • are between the ages of 20 and 292
  • have a family member, most often a sibling or parent, with IBD
  • are of Jewish descent2
  • smoke cigarettes

What are the complications of Crohn’s disease?

Crohn’s disease may lead to complications that develop over time. Complications may include

The inflammation of Crohn’s disease may lead to serious complications, which could require being treated at a hospital or surgery. Serious complications include

  • intestinal obstruction, a partial or total blockage of the movement of food, fluid, air, or stool through your intestines.
  • fistulas, which are abnormal passages or tunnels between two organs, or between an organ and the outside of your body. Fistulas may become infected.
  • abscesses, which are painful, swollen, pus-filled pockets of infection.
  • anal fissures, which are small tears in your anus. Anal fissures may cause itching, pain, or bleeding.
  • ulcers, or open sores in your mouth, intestines, anus, or perineum.

Health problems affecting other parts of the body

Some people with Crohn’s disease also have inflammation in parts of the body other than the digestive tract, including the

People with Crohn’s disease also commonly report stress, depression, and anxiety. Stress may change the microbiome in the digestive tract, which can worsen the symptoms of Crohn’s disease.

Colorectal and small intestine cancer

If you have Crohn’s disease in your large intestine, you are more likely to develop colorectal cancer. Your risk is higher if you’ve had Crohn’s disease for a longer time. Your risk is also higher if you have PSC or a family history of colorectal cancer.

Your doctor may recommend a colonoscopy to screen for colorectal cancer. Screening is testing for diseases when you have no symptoms. Screening can check for colorectal cancer or precancerous cells, known as dysplasia. Diagnosing cancer early can improve chances for recovery.

For people with Crohn’s disease in the large intestine, doctors most often recommend starting colorectal cancer screening 8 to 10 years after diagnosis. Doctors may recommend repeat screening every 1 to 5 years.3,4 If you have Crohn’s disease and PSC, your doctor may recommend screening every year, starting at diagnosis.2

If you have Crohn’s disease in your small intestine, you may be more likely to develop small intestine cancer, but the risk is very low.

References

Last Reviewed July 2024
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This content is provided as a service of the National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK), part of the National Institutes of Health. NIDDK translates and disseminates research findings to increase knowledge and understanding about health and disease among patients, health professionals, and the public. Content produced by NIDDK is carefully reviewed by NIDDK scientists and other experts.