Description

A benign, inherited syndrome in which mild, intermittent unconjugated hyperbilirubinemia occurs in the absence of hemolysis or liver dysfunction

Pediatric Considerations
Rare for the disorder to be diagnosed before puberty

Pregnancy Considerations
The relative fasting that may occur with morning sickness can elevate bilirubin level.

Epidemiology

• Predominant age: present from birth but most often presents in the 2nd or 3rd decade of life
• Predominant sex: male > female (2 to 7:1)

Prevalence
Prevalence in the United States: ~8% of the population; ~1 in 3 of those affected are not aware that they have the disorder.

Etiology and Pathophysiology

Indirect hyperbilirubinemia in Gilbert syndrome (GS) results from impaired hepatic bilirubin clearance (~30% of normal) due to decreased levels of the enzyme uridine diphosphoglucuronate-glucuronosyltransferase (UDPGT). Hepatic bilirubin conjugation (glucuronidation) is thus reduced, although this may not be the only defect.

Genetics

• Inherited defects within the promoter region of the gene that encodes the enzyme UDPGT yields reduced conjugation of bilirubin with glucuronic acid.
• Once considered as an autosomal dominant condition, GS is now thought to be inherited in an autosomal recessive manner.

Risk Factors

• Male gender
• Family history; particularly first-degree relatives

Commonly Associated Conditions

GS is part of a spectrum of hereditary disorders that includes types I and II Crigler-Najjar syndrome (1). However, bilirubin levels in these cases will be >6 mg/dL.