Primary Sclerosing Cholangitis (PSC)
- Primary Sclerosing Cholangitis (PSC) is a disease of unknown etiology and pathogenesis which leads to inflammatory obliteration of both the intra-hepatic and extra-hepatic biliary tree.
- A primarily lymphocytic infiltrate is observed around both extra-hepatic and intra-hepatic bile ducts. Over time, a progressive ringing fibrosis surrounds the atrophying bile ducts, termed "Onion-skin Fibrosis", leading to their narrowing and ultimately total obliteration. These morphological changes occur in a segmental pattern, leaving areas of intervening normal bile duct which then undergo morphological changes associated with cholestasis due to intra-luminal build up of bile (See: cholestasis). Eventually a picture of cirrhosis similar to that of secondary biliary cirrhosis emerges.
- Over 50% of patients with PSC also possess Ulcerative Colitis. Note however that only 4% of patients with Ulcerative Colitis possess PSC.