In patients with ATP8B1 deficiency, the asymmetry of aminophospholipids in the hepatocanalicular membrane is disrupted, and the transport activity of the bile acid transport pump, which is an ABC transporter localized on the hepatocanalicular membrane that mediates the excretion of bile acids, is reduced, thus resulting in the development of severe intrahepatic cholestasis (7, 8). Here, ABCG2 is linked to intrahepatic cholestasis.