ATP8B1 and progressive familial intrahepatic cholestasis: Based on laboratory findings, liver histology, and causative genes, PFIC is classified into three types: PFIC 1, caused by mutations in the ATP8B1 gene, encoding FIC 1 (Familial Intrahepatic Cholestasis 1) protein, PFIC 2, caused by mutations in the ABCB11 gene (ATP-binding cassette family B) encoding the bile salt export pump (BSEP), and PFIC3, caused by mutations in the ABCB4 gene encoding the Multidrug Resistance 3 (MDR3) protein on chromosome 7q21 [5].