ABCB4 and primary biliary cholangitis: Homozygous and heterozygous mutations in the MDR3 (now referred to as ABCB4) gene, the phosphatidylcholine translocator across the canalicular membrane, are thought to be responsible for progressive intrahepatic cholestasis type 3 (PFIC 3) [7], and heterozygous mutations have been also reported in patients presenting with a history of intrahepatic cholestasis of pregnancy or with a cholangiopathy referred to as anti-mitochondrial antibody (AMA) negative primary biliary cirrhosis (PBC) [8-11].