Definition & Facts of Microscopic Colitis

In this section:

What is microscopic colitis?

Microscopic colitis is a chronic disease in which abnormal reactions of the immune system cause inflammation on the inner lining of your colon. Doctors can only see this inflammation by looking at colon tissue under a microscope.

Microscopic colitis is an inflammatory bowel disease (IBD). Crohn’s disease and ulcerative colitis are other common types of IBD. Unlike the other types of IBD, microscopic colitis does not increase your risk of developing colon cancer.

Two types of microscopic colitis are lymphocytic colitis and collagenous colitis. The two types cause different changes in colon tissue.

  • In lymphocytic colitis, the colon lining contains more white blood cells than normal. The layer of collagen under the colon lining is normal or only slightly thicker than normal.
  • In collagenous colitis, the layer of collagen under the colon lining is thicker than normal. The colon lining may also contain more white blood cells than normal.

Doctors call both types microscopic colitis, and they have the same symptoms and treatments.

Health care professional using a microscope.Doctors can only see the inflammation caused by microscopic colitis by looking at colon tissue under a microscope.

How common is microscopic colitis?

Research suggests that, in the United States, about 700,000 people have microscopic colitis.1

Who is more likely to have microscopic colitis?

Anyone can develop microscopic colitis. The disease is more common in

  • older adults. The average age at which people are diagnosed with microscopic colitis is 60 to 65 years.2 However, microscopic colitis may occur in people of any age, including children.
  • women. Research suggests the disease is three to nine times more common in women than in men.2
  • people who have certain immune disorders.
  • people who smoke.
  • people who take medicines that have been linked to an increased risk for microscopic colitis.

What other health problems do people with microscopic colitis have?

Experts have found that some people with microscopic colitis also have other disorders related to the immune system. These disorders include

What are the complications of microscopic colitis?

Compared with other types of IBD, microscopic colitis is less likely to lead to complications. If microscopic colitis causes severe diarrhea, it may lead to weight loss and dehydration. In rare cases, microscopic colitis may cause serious complications, such as ulcers or perforation of the colon.


Last Reviewed April 2021
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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.