ABCB11 and progressive familial intrahepatic cholestasis type 1: Based on laboratory findings, liver histology, and causative genes, PFIC is usually classified into three types: PFIC-1, also known as Byler's disease, is caused by mutations in the ATP8B1 gene encoding the familial intrahepatic cholestasis 1 (FIC1) protein [2]; PFIC-2, also previously known as Byler's syndrome [3], is caused by mutations in the ABCB11 gene (ATP-binding cassette [ABC] family B) encoding the bile salt export pump (BSEP) [4]; PFIC-3 is caused by mutations in the ABCB4 gene encoding a multidrug resistance class 3 (MDR3) protein.