Autoimmune hepatitis (AIH)
This is an autoimmune disease where the attack is on the hepatocytes (cells of the liver) rather than the biliary cells (bile ducts). It presents very differently and is treated very differently as well. When both diseases are present this is called 'AIH overlap'.
One can have 100% PBC and move to 100% AIH and back again. In the past many were labelled as having AIH when they've really had a more aggressive form of PBC. They have very similar AIH- like features.