Hyperbilirubinemia

Gilbert disease and Crigler-Najjar syndromes result in unconjugated hyperbilirubinemia caused by deficiency of bilirubin-UDP-glucuronosyltransferase which is involved in the detoxification of bilirubin by conjugation with glucuronic acid. Gilbert disease is a benign familial disorder characterized by low-grade chronic hyperbilirubinemia, while Crigler-Najjar syndromes are more severe by kernicterus and jaundice. Dubin-Johnson syndrome (DJS) is caused by mutations in ABCC2, a canalicular bilirubin glucuronide and xenobiotic export pump. Rotor syndrome (RS) is caused by mutations in the SLCO1B1 and SLCO1B3 genes that encode organic anion transporters. In both DJS and RS, mild jaundice begins shortly after birth or in childhood. There are no signs of hemolysis, and routine hematologic and clinical-biochemistry test results are normal, aside from the primarily conjugated hyperbilirubinemia. The hepatocyte pigment deposits are typical of DJS. Total urinary excretion of coproporphyrins is greatly increased in RS.