Primary Sclerosing Cholangitis (PSC) is a chronic liver disease, in which the walls of the bile ducts, inside and outside the liver, become inflamed. This creates a build-up of bile in the liver, leading to potentially serious complications. The exact cause of PSC is unknown, although it is believed to be caused by changes in the immune system. It generally strikes men between the ages of 30 and 60 and is more common in people who also have ulcerative colitis.