Abstract
Defects in transport proteins that are expressed at the hepatocyte canalicular membrane can cause severe impairment of hepatobiliary transport processes. Progressive familial intrahepatic cholestasis (PFIC) typically manifests in early childhood. Genetic variants in the aminophospholipid transporter FIC1 (ATP8B1 gene) cause PFIC1, characterized by elevated serum bile acids but normal or only mildly elevated gamma-GT levels. Benign recurrent intrahepatic cholestasis type 1 (BRIC1) is also caused by ATP8B1 mutations. Defects in the function of the bile salt efflux pump (BSEP, ABCB11) cause PFIC2 or BRIC2, depending upon the degree of BSEP impairment. A common BSEP variant, the V444A polymorphism, is commonly found in various types of cholestatic liver injury including drug-induced liver injury (DILI). Finally, dysfunction of the multidrug resistance gene product MDR3 (ABCB4) leads to PFIC3, characterized by low biliary phospholipids and high gamma-GT levels in serum due to bile duct injury. All three transporter genes are also associated with intrahepatic cholestasis of pregnancy. Treatment options include UDCA for milder forms, or liver transplantation for severe pediatric cases.
Mwinyi, J