ABCB4 and portal hypertension: The ABCB4 variants in this study impaired the floppase function of the MDR3 protein, and thus the depletion of phosphatidylcholine and elevation of hydrophobic bile acids in the biliary tubules damaged the integrity of the cholangiocyte membrane, leading to the development of intrahepatic cholestasis and presenting as hepatomegaly, pruritus, splenomegaly, jaundice and portal hypertension.