PSC disease causes

My friend is suffering from Primary Sclerosing Cholangitis so can you please tell me the causes of this?

[Pathak]

Primary sclerosing cholangitis (PSC) is a chronic (lasting years and decades), progressive (worsening over time) disease of the bile ducts that channel bile from the liver into the intestines.

Primary sclerosing cholangitis (PSC) is a chronic liver disease caused by scarring of the bile ducts and progressive inflammation.

In primary sclerosing cholangitis, the intrahepatic and extrahepatic bile ducts become inflamed, scarred and thickened (sclerotic), narrowed, and finally obstructed.