A systemic review of association between UDP glucuronosyltransferase family 1 member A1 (UGT1A1) polymorphisms in Gilbert's syndrome in Sickle Cell Disease

Abstract

Gilbert's syndrome (GS) is a benign hereditary disorder of bilirubin metabolism due to a mutation in the UDP glucuronosyltransferase family 1 member A1 (UGT1A1) gene which results in hyperbilirubinaemia and related complications mainly cholelithiasis. It can be co-inherited along with sickle cell anaemia, thalassaemias and other haemoglobinopathies including glucose-6-phosphate dehydrogenase deficiency, hereditary spherocytosis and cystic fibrosis. More than 100 mutations have been reported in UGT1A1 gene and the most common as insertion of extra (TA) nucleotides in the promoter region of TATA box. The more the number of TA repeats, the higher is the bilirubin levels. These mutations result in a 10%–35% reduction in the UGT1A1 enzyme activity resulting in mild to moderate unconjugated hyperbilirubinaemia and related complications. For diagnosis the mode of inheritance is more important than testing in the patients. However; the inheritance pattern of GS differs in ethnicities. For early diagnosis to prevent worsening of the symptoms and for timely management one should be aware of the inheritance pattern in patient. In this systemic analysis we studied the association between complications in GS with the genotypes and complications. It was found that TA7/7 is more significant in GS with sickle cell disease (SCD) group when compared to healthy controls with 2.2% chances of having this genotype in GS with SCD than healthy controls. The significance of having TA7/7 genotype is similar in GS with SCD and α-thalasaemia group. However, there is a high recommendation to carry out multicentre studies and conduct meta-analyses for establishing universal recommendations.