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Key Features

  • Common form of familial hyperbilirubinemia present in 3–7% of the population

  • Males are affected more often than females (4:1)

  • Associated with a partial reduction of hepatic bilirubin uridine diphosphate-glucuronyl transferase activity

  • Can occur following liver transplantation

Clinical Findings

  • Affected infants may have more rapid increase in jaundice in the newborn period, accentuated breast milk jaundice, and jaundice with intestinal obstruction

  • During puberty and beyond, mild fluctuating jaundice, especially with illness and vague constitutional symptoms, is common

  • Shortened red blood cell survival in some patients is thought to be caused by reduced activity of enzymes involved in heme biosynthesis (protoporphyrinogen oxidase)

  • Serum unconjugated bilirubin is generally < 3–6 mg/dL, although unusual cases may exceed 8 mg/dL


  • Findings on liver biopsy and most liver function tests are normal

  • An increase of 1.4 mg/dL or more in the level of unconjugated bilirubin after a 2-day fast (300 kcal/d)

  • Genetic testing is available but rarely needed


  • No treatment is necessary

  • Phenobarbital (5–8 mg/kg/d) can reduce hyperbilirubinemia, but therapy is not justified

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