Interpretation
Gilbert’s syndrome is caused by reduced activity of the uridine diphosphoglucose glucuronyltransferase enzyme (UGT1A1), resulting from the inheritance of two mutant alleles of the gene. It results in low-grade non-haemolytic unconjugated hyperbilirubinaemia, without other biochemical or clinical features of hepatic pathology. In Caucasians, Gilbert’s syndrome is almost exclusively due to the dual inheritance of alleles with a two base insertion in the promoter sequence for the UGT1A1 gene. The TA(7)TAA variant, also referred to as the UGT1A1*28 variant, occurs in the population at a frequency of 30% while the normal TA(6)TAA allele has a frequency of 70%. This leads to a prevalence of Gilbert’s syndrome of approximately 5%.
Test Method
Fluorescently tagged PCR fragments from the UGT1A1 promoter region at 2q37 are accurately sized on the ABI3130xl Genetic Analyser.
