Abstract
Serum bilirubin concentrations are increased in several hematological and hepatic disorders; however, hyperbilirubinemia, often of familial origin, may occur without overt signs of hemolysis or evident liver disease. The authors review briefly the main steps of hepatic bilirubin metabolism, then discuss the pathogenetic mechanisms of the different forms of familial hyperbilirubinemia. The knowledge of these conditions is increasingly important because orthotopic liver transplantation may be a therapeutic choice for some severe forms. Furthermore, early diagnosis is necessary to avoid unnecessary medical investigations for the otherwise relatively common, benign unconjugated hyperbilirubinemia. Finally, individuals with unmasked defective bilirubin handling may be potential liver donors; thus, unexplained jaundice occurring after orthotopic liver transplantation may be related to this disorder.