Gilbert syndrome is characterized by mild, chronic, unconjugated hyperbilirubinemia in the absence of liver disease or overt hemolysis and is found in approximately 3-10% of the general population. The diagnosis of this disorder is made on the observation of elevated unconjugated bilirubin levels and normal liver function. The importance of the diagnosis of this benign syndrome is to rule out more serious liver disease as the underlying cause of the hyperbilirubinemia.
Gilbert syndrome is generally considered to be an autosomal recessive disorder. However there have been cases of heterozygosity reported in patients with Gilbert syndrome, particularly in the Asian population. A polymorphism in the promoter region of the UGT1A1 gene, A(TA)7TAA, has been identified in the majority of Caucasian individuals with Gilbert syndrome (80-100%). A missense change in the UGT1A1 gene, G71R, has been identified in approximately 30-40% of Asian individuals with neonatal hyperbilirubinemia and has been implicated in Gilbert syndrome in this population. Any samples that are not homozygous for the A(TA)7TAA allele will also be tested for the G71R polymorphism.