Nonhemolytic hyperbilirubinemias.

The familial nonhemolytic hyperbilirubinemias include the syndromes of Gilbert, Crigler-Najjar, Dubin-Johnson and Rotor. Gilbert's syndrome is probably very common in occult form, and patients come to clinical attention partially owing to subtle coincidental hemolysis. The biochemical defect may lie not in microsomal glucuronyl transferase but rather in the plasma membrane enzyme which transglucuronidates bilirubin monoglucuronide to diglucuronide. Patients with Crigler-Najjar type I, a severe disease, exhibit virtual absence of glucuronyltransferase. Type II is milder and appears related to Gilbert's syndrome. Dubin-Johnson's syndrome and Rotor's syndrome, the conjugated hyperbilirubinemias, are separate entities. The former is a block in hepatic excretion, while the defect in the latter lies at least partially in uptake of bilirubin.