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

• anemia, a condition in which you have fewer red blood cells than normal. Crohn’s disease may lead to more than one type of anemia, including iron-deficiency anemia NIH external link, anemia of inflammation or chronic disease, or vitamin B12 deficiency anemia NIH external link.
• bone problems. Crohn’s disease and corticosteroids NIH external link used to treat the disease may lead to low bone mass NIH external link, known as osteopenia or osteoporosis NIH external link.
• problems with growth and development in children. Problems may include gaining less weight than normal, slowed growth, short stature, or delayed puberty NIH external link.
• malnutrition, a condition in which you don’t get enough of the vitamins, minerals, and other nutrients you need to be healthy.

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 NIH external link, a partial or total blockage of the movement of food, fluid, air, or stool through your intestines.
• fistulas NIH external link, which are abnormal passages or tunnels between two organs, or between an organ and the outside of your body. Fistulas may become infected.
• abscesses NIH external link, 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

• joints, causing certain types of arthritis
• skin, such as a rash that can be painful
• eyes, including irritation
• liver and bile ducts, causing conditions such as primary sclerosing cholangitis (PSC)
• kidneys, including development of kidney stones
• lungs, which if severe can lead to difficulty breathing

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 NIH external link. 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 NIH external link, but the risk is very low.

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