Loss-of-function mutations in the hepatocyte canalicular phospholipid flippase MDR3 (ABCB4) have been associated with a wide range of human biliary diseases including progressive familial intrahepatic cholestasis type 3 (PFIC3), cholestasis of pregnancy, drug induced cholestasis and an adult biliary cirrhosis with features similar to primary sclerosing cholangitis (PSC) [4], [5], [6], [7]. Here, ABCB4 is linked to progressive familial intrahepatic cholestasis type 3.