ABCB4 and progressive familial intrahepatic cholestasis: Other forms of PFIC include PFIC1 caused by variants in the ATP8B1 gene [18], PFIC3 caused by variants in the ABCB4 gene [19,20], PFIC4 caused by variants in the TJP2 gene [21,22], PFIC5 caused by variants in the NR1H4 gene [23] and PFIC6 caused by variants in the MYO5B gene [24,25,26].