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. 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.
• people who have certain immune disorders.
• people who smoke.
• people who take medicines that have been linked to an increased risk for microscopic colitis.

Doctors aren’t sure what causes microscopic colitis. Experts think the following factors may play a role in causing or increasing the risk for microscopic colitis.

Abnormal immune reactions

Abnormal reactions of the immune system may play a role in causing microscopic colitis. Abnormal immune reactions lead to inflammation in the colon.

People who have certain immune disorders—such as celiac disease, rheumatoid arthritis, or type 1 diabetes—are more likely to develop microscopic colitis. Scientists are studying the links between microscopic colitis and these immune disorders.

Genes

Research suggests certain genes increase the chance a person will develop microscopic colitis.

Medicines

Taking certain medicines may increase the risk of developing microscopic colitis. These medicines include

• nonsteroidal anti-inflammatory drugs (NSAIDs)
• proton pump inhibitors (PPIs)
• selective serotonin reuptake inhibitors (SSRIs), a type of antidepressant
• hormone replacement therapy and oral contraceptives
• beta blockers, medicines that slow your heart rate
• statins, medications to lower cholesterol

Smoking

Studies suggest people who smoke cigarettes are more likely to develop microscopic colitis. Among people who develop microscopic colitis, those who smoke tend to develop the disease at a younger age.

Other factors

Researchers are studying other factors that may play a role in causing or worsening microscopic colitis. These factors include

• bile acid malabsorption—in which the small intestine doesn’t absorb enough bile acid and extra bile acid passes into the colon
• changes in the microbiome
• female hormones
• infections
• body mass index

To help diagnose microscopic colitis, your doctor will ask about your symptoms and medical history and will perform a physical exam. Your doctor may ask about factors that increase the risk of developing microscopic colitis, such as smoking or taking certain medicines.

Your doctor may order medical tests, such as blood and stool tests, to check for signs of conditions that cause symptoms similar to those of microscopic colitis. Conditions that cause similar symptoms include celiac disease, other types of inflammatory bowel disease (IBD), and infections.

Colonoscopy with biopsies

Doctors order a colonoscopy with biopsies to diagnose microscopic colitis and rule out other digestive conditions.

During a colonoscopy, doctors use a colonoscope or scope—a long, flexible, narrow tube with a light and tiny camera on one end—to view the lining of the colon. The colon lining most often appears normal in people who have microscopic colitis.

Doctors obtain biopsies by passing an instrument through the colonoscope to take small pieces of tissue from the lining of your colon. To diagnose microscopic colitis, a pathologist will examine the tissue under a microscope to check for signs of the disease.

• Dietary changes such as a reduced-fat diet and/or eliminating foods that contain caffeine and lactose.
• Avoiding or discontinuing medications that some people have reported triggered the disease (such as NSAIDS and proton pump inhibitors).
• Antidiarrheal medications such as loperamide.
• Corticosteroids such as budesonide.
• Anti-TNF therapies such as infliximab and adalimumab.
• Surgery to remove all or part of the colon in severe cases that to not respond to other treatment options.