Gilbert syndrome (GS) is the most common aetiology of hereditary jaundice.[6]Sticova E, Jirsa M. New insights in bilirubin metabolism and their clinical implications. World J Gastroenterol. 2013 Oct 14;19(38):6398-407.
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3801310
http://www.ncbi.nlm.nih.gov/pubmed/24151358?tool=bestpractice.com
Incidence of GS is approximately 6%.[7]Owens D, Evans J. Population studies on Gilbert's syndrome. J Med Genet. 1975 Jun;12(2):152-6.
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC1013257
http://www.ncbi.nlm.nih.gov/pubmed/1142378?tool=bestpractice.com
Population studies show that GS is more common in men, with a male-to-female ratio ranging from 2:1 to 7:1.[8]Watson KJ, Gollan JL. Gilbert's syndrome. Baillieres Clin Gastroenterol. 1989 Apr;3(2):337-55.
http://www.ncbi.nlm.nih.gov/pubmed/2655758?tool=bestpractice.com
An estimated one third of individuals with GS remain undiagnosed due to the asymptomatic nature of the condition.[1]Claridge LC, Armstrong MJ, Booth C, et al. Gilbert's syndrome. BMJ. 2011 Apr 19;342:d2293.
http://www.ncbi.nlm.nih.gov/pubmed/21508045?tool=bestpractice.com
Worldwide prevalence is difficult to discern, as diagnostic criteria depend on numerous factors, including levels of bilirubin; number of times bilirubin level is analysed; and whether the patient was fasting, is medicated, or has used alcohol. All of these factors may affect bilirubin concentration. One study in Middle Eastern populations showed that parents of neonates with indirect hyperbilirubinaemia of unknown aetiology showed no difference in the prevalence of GS when compared with parents of neonates with normal bilirubin.[9]Saki F, Hemmati F, Haghighat M. Prevalence of Gilbert syndrome in parents of neonates with pathologic indirect hyperbilirubinemia. Ann Saudi Med. 2011 Mar-Apr;31(2):140-4.
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3102472
http://www.ncbi.nlm.nih.gov/pubmed/21403409?tool=bestpractice.com
GS occurs in people of all races. Molecular studies show that the clinical phenotype of GS can be described by polymorphisms in the TATA box promoter of the UGT1A1 gene. This polymorphism is found in up to 36% of Africans, but only 3% of Asians.[10]Burchell B, Hume R. Molecular genetic basis of Gilbert's syndrome. J Gastroenterol Hepatol. 1999 Oct;14(10):960-6.
http://www.ncbi.nlm.nih.gov/pubmed/10530490?tool=bestpractice.com
A second common mutation leading to the Gilbert phenotype is located in exon 1 of the UGT1A1 gene and is found more commonly in Japanese and Asian populations.[10]Burchell B, Hume R. Molecular genetic basis of Gilbert's syndrome. J Gastroenterol Hepatol. 1999 Oct;14(10):960-6.
http://www.ncbi.nlm.nih.gov/pubmed/10530490?tool=bestpractice.com
[11]Takeuchi K, Kobayashi Y, Tamaki S, et al. Genetic polymorphisms of bilirubin uridine diphosphate-glucuronosyltransferase gene in Japanese patients with Crigler-Najjar syndrome or Gilbert's syndrome as well as in healthy Japanese subjects. J Gastroenterol Hepatol. 2004 Sep;19(9):1023-8.
http://www.ncbi.nlm.nih.gov/pubmed/15304120?tool=bestpractice.com