Causes

It's not clear what causes primary sclerosing cholangitis. An immune system reaction to an infection or toxin may trigger the disease in people who are genetically predisposed to it.

A large proportion of people with primary sclerosing cholangitis also have inflammatory bowel disease, an umbrella term that includes ulcerative colitis and Crohn's disease.

Primary sclerosing cholangitis and inflammatory bowel disease don't always appear at the same time, though. In some cases, primary sclerosing cholangitis is present for years before inflammatory bowel disease occurs. If primary sclerosing cholangitis is diagnosed, it's important to look for inflammatory bowel disease because there is a greater risk of colon cancer.

Somewhat less often, people being treated for inflammatory bowel disease turn out to have primary sclerosing cholangitis as well. And rarely, people with primary sclerosing cholangitis develop inflammatory bowel disease only after having a liver transplant.