Cause
The exact cause of primary sclerosing cholangitis is  unknown, and its pathogenesis is improperly understood. Although PSC is thought to be caused by autoimmune disease, it does not demonstrate a clear response to immunosuppressants. Thus, many experts believe it to be a complex, multifactorial (including immune-mediated) disorder and perhaps one that encompasses several different hepatobiliary diseases.Data have provided novel insights suggesting:

an important association between the intestinal microbiota and PSC and
a process referred to as cellular senescence and the senescence-associated secretory phenotype in the pathogenesis of PSC.In addition, longstanding, well-recognized associations are seen between PSC and human leukocyte antigen alleles (A1, B8, and DR3). Pathophysiology
PSC is characterized by inflammation of the bile ducts (cholangitis) with consequent stricturing (i.e., narrowing) and hardening (sclerosis) of these ducts due to scar formation, be it inside and/or outside the liver. The resulting scarring of the bile ducts obstructs the flow of bile, which further perpetuates bile duct and liver injury. Chronic impairment of bile flow due to blockage and dysfunctional bile transport (cholestasis) causes progressive biliary fibrosis and ultimately biliary cirrhosis and liver failure.The primary physiological function of bile is to assist in the breakdown and absorption of fat in the intestinal tract; a relative deficiency of bile can lead to fat malabsorption and deficiencies of fat-soluble vitamins (A, D, E, K).Liver enlargement is seen due to portal hypertension caused by compression of portal veins by the proximate sclerosed intrahepatic bile ducts, and leads to right upper quadrant abdominal pain.
Obeticholic acid is being investigated as a possible treatment for PSC due to its antifibrotic effects. Simtuzumab is a monoclonal antibody against the profibrotic enzyme LOXL2 that is being developed as a possible therapy for PSC. Notable cases
Chris Klug – professional snowboarder with PSC who had liver transplant
Chris LeDoux – professional rodeo rider and country musician with PSC who died of cholangiocarcinoma
Elena Baltacha – British professional tennis player, diagnosed with PSC at age 19 and died five months after being diagnosed with PSC-associated liver cancer (specifically cholangiocarcinoma) at the age of 30
Walter Payton – died of complications of PSC
Kieron Dyer – professional footballer
James Redford – director and son of Robert Redford who underwent two liver transplants due to PSC

References
External links
Patient support organizations:

www.pscpartners.org—based in the US
www.pscpartners.ca—based in Canada
www.pscsupport.org.au—based in Australia
www.pscsupport.org.uk—based in the UK