ABCB4 and hyperinsulinemic hypoglycemia, familial, 4: Rare genetic hepatobiliary diseases, such as PFIC2 (ABCB11/BSEP deficiency) and progressive familial intrahepatic cholestasis type 3 (PFIC3) (ABCB4/MDR3 deficiency) highlight the importance of apposite BA handling in maintaining both liver and biliary health.