The hereditary hyperbilirubinemias include those resulting in predominantly unconjugated hyperbilirubinemia: Gilbert or Arias syndrome, Crigler-Najjar syndrome type I, and Crigler-Najjar syndrome type II; and those resulting in predominantly conjugated hyperbilirubinemia: Dubin-Johnson syndrome, Rotor syndrome, and several forms of intrahepatic cholestasis. Detailed studies show that patients with Crigler-Najjar syndrome type II have reduced activity of bilirubin glucuronosyltransferase. [From OMIM]