Inheritance: autosomal dominant with incomplete penetrance
Basis: impaired hepatic UDP-glucuronosyl transferase activity, but present
Most patients are identified during adolescence or as a young adult, due to either jaundice or an elevated serum bilirubin concentration. The patients are often asymptomatic, but some may experience fatigue, malaise or nonspecific symptoms.
Bilirubin findings:
(1) intermittent hyperbilirubinemia, with at least 2 occasions over 6 months
(2) no bilirubinuria
(3) conjugated (direct) bilirubin represents < 20% of the total bilirubin
Exclusions:
(1) no evidence of liver disease (normal GGT, transaminases, albumin, prothrombin time and liver biopsy)
(2) no evidence of hemolysis (normal serum hemoglobin, reticulocyte count, haptoglobin, and blood smear morphology)
NOTE: Because of the frequency of Gilbert's syndrome, a patient may have it together with a common liver or hematologic condition. Diagnosis of the Gilbert's syndrome then requires evaluation after recovery from the other condition.
Increases in total bilirubin may follow:
(1) caloric restriction (fasting with < 400 calories a day for 72 hours causes increases in serum unconjugated bilirubin in 100% of patients)
(2) carbohydrate load
(3) nicotinic acid
(4) physical exercise
(5) stress
(6) febrile illness
(7) menstruation or pregnancy
(8) birth control pills
(9) alcohol
Decrease in total bilirubin may follow:
(1) return to a normal diet after fasting
(2) administration of phenobarbital or other liver enzyme inducing agents
(3) administration of prednisone
