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. Individuals with Gilbert syndrome have a reduced level of hepatic bilirubin UDP-glucuronosyltransferase 1A1 (UGT1A1), the enzyme necessary for the conjugation of bilirubin. This enzyme is encoded for by the UGT1A1 gene on chromosome 2q37.
Gilbert syndrome is generally considered to be an autosomal recessive disorder. 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%). This change is associated with reduced expression of the UGT1A1 gene and thereby reduced levels of the UGT1A1 protein. The frequency of the A(TA)7TAA allele is approximately 40% in the general population. The A(TA)7TAA allele is also known as UGT1A1*28. However there have been cases of heterozygosity reported in patients with Gilbert syndrome, particularly in the Asian population. 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.
The combination of normal blood and liver function tests and elevated bilirubin levels is an indicator of Gilbert's syndrome. The importance of the diagnosis of this benign syndrome is to rule out more serious liver disease as the underlying cause of the hyperbilirubinemia. However, as the diagnosis is largely one of exclusion, it is sometimes difficult to dispel lingering fears of serious liver disease, causing patients unwarranted anxiety. Genetic testing confirms the diagnosis.
Genetic counselling of Gilbert syndrome patients is offered at CMG.
Detection: We offer DNA test for the detection of A(TA)7TAA promotor polymorphism of UGT1A1 gene specific for the Caucasian population using the PCR-amplification technique and sizing by polyacrylamide gel-electrophoresis.
Specimen Requirements: genomic DNA is isolated from the peripheral blood, collected in 2 ml EDTA Vacutainer tube (lavender top). In case if DNA is already extracted, the minimum concentration should be 25 ng/µl.
Transportation: The blood specimen can be stored in the refrigerator (for 1 or 2 days) and shipped to CMG at room temperature. In case of the DNA, it can be shipped to CMG at room temperature within 1-2 days.
Turnaround time: 10-15 days
For further information please contact:
Tel.: (+374 10) 544367
Fax: (+374 10) 544366