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Key Features

  • Type 1: rapid severe unconjugated hyperbilirubinemia (> 30–40 mg/dL) with neurologic consequences (kernicterus)

  • Type 2

    • Milder than type 1

    • Rarely associated with neurologic complications

Clinical Findings

  • Type 1

    • Consanguinity is often present

    • Neurologic signs may not develop until adolescence or early adulthood, at which time deterioration may occur suddenly

  • Type 2

    • Hyperbilirubinemia is less severe

    • Bile is pigmented and contains small amounts of bilirubin monoglucuronide and diglucuronide


  • Type 1

    • May be useful to obtain a duodenal bile specimen; findings include

      • Being colorless

      • Containing a predominance of unconjugated bilirubin, small amounts of monoconjugates, and only traces of unconjugated bilirubin

  • Liver biopsy findings and liver function tests are consistently normal

  • Type 2

    • Liver biopsy findings and liver function tests are consistently normal


  • Type 1

    • Exchange transfusions are required followed by phototherapy

    • A combination of aggressive phototherapy and cholestyramine may keep bilirubin levels below 25 mg/dL

    • Orlistat therapy may decrease bilirubin in a subset of patients

    • Liver transplantation is curative and may prevent kernicterus if performed early

    • Auxiliary orthotopic transplantation also relieves the jaundice while the patient retains native liver

  • Type 2

    • Phenobarbital (4 mg/kg/d in infants) lowers serum bilirubin levels

    • An increased proportion of monoconjugated and diconjugated bilirubin in the bile follows phenobarbital treatment

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