UGT1A1 Gene And Clinical Features Of Hereditary Unconjugated Hyperbilirubinemia

Objective: to investigate the clinical,genetic features and prognosis of hereditary unconjugated hyperbilirubinemia in children.Methods:1.Clinical and liver function data of children who had high indirect bilirubinemia for nearly 5 years were collected and included into the observation group after meeting the standards who had been admitted to the digestive and liver disease specialty of Department of Pediatrics,Second Hospital of Hebei Medical University.Peripheral blood DNA from children and their parents were collected for UGT1A1 gene test.All the children were followed up regularly.2.Case inclusion criteria:Children whose age were greater than one month,their indirect bilirubin were greater than 51.3umol/L(3 times normal level)were included.According to the history of jaundice,the liver function was mainly increased by indirect bilirubin(IBIL),and slightly elevated or normal by direct Bilirubin(DBIL).Hemolytic factors,digestive tract structure factors,infection factors and immune factors were excluded.3.Genetic testing method: DNA was extracted from the peripheral blood of the probands.Relevant exons and side intron regions were amplified by PCR,and then Sanger sequencing was performed.The sequencing results were compared with the standard reference sequence.If a mutation is detected,the parents of the proband are targeted to detect the mutation origin.Results:All the 11 children had mutations in UGT1A1 gene.A total of 6mutations were detected,including:c.211G>A;c.378C>G;c.563T>G;c.1091C>T;c.1456T>G;A(TA)6TAAins TA.Two new mutations of UGT1A1 gene were found worldwide in this study:c.378C>G(Exon1);c.563T>G(Exon1).More mutations happened in the exon region(94.7%)were confirmed in Asians.Among the 11 cases,5 cases were homozygous mutation(45.4%);3cases were complex heterozygous mutation(27.3%);3 cases were singlestrand heterozygous mutation(27.3%).The main clinical manifestation at the onset was jaundice in 11 cases.The onset age ranged from 1 month to 13 years old,the median age was 2 months old with an average of 2.5±4.1years old.The level of indirect Bilirubin when onset was 46.5-161.0umol/L(mean 94.1±32.5umol/L).Transaminase,bile acid and γ-glutamyl transpeptidase had no significant changes.The indirect bilirubin ranged from 5.1 to 68.0umol/L with an average of 28.5±18.2umol/L after 6 months.The indirect bilirubin level improved after 6 months.5 Five children with c.1456T>G(p.Y486D)homozygous mutation had significantly increased indrict bilirubin level at onset time with an average of79.5±31.2umo/L.The indirect bilirubin level decreased after 6 months,but remained higher than the normal level with an average of 39.6±8.1umo/L.Intelligence and physical development did not affected.Indirect bilirubin in 1 child with c.563A>C/A(TA)6TAAins TA mutation was significantly elevated at onset with 116.8umo/L.6 months later,indirect bilirubin decreased to 61.0umo/L,still significantly higher than normal.The indirect bilirubin level in the remaining 5 children decreased to normal after 6months.Three cases of c.1456T>G homozygous children were followed up for2-8 years,four hepatic fibrosis indexes were all within the normal range.Conclusion:1.Two new mutations of UGT1A1 gene were found worldwide in this study: c.378C>G(Exon1);c.563T>G(Exon1).More mutations happened in the exon region(94.7%)were confirmed in Asians.2.The top three common mutations in this study were:c.1456T>G(44.4%);c.211G>A(25.9%);c.1091C> T(11.1%).3.Children with UGT1A1 gene mutation can develop hyperindirect bilirubinemia,but there is no significant effect on transaminase,bile acid andγ-glutamyl transpeptidase.6 months later,indirect bilirubin returned to normal in some children.4.The level of indirect bilirubin in children with homozygous mutation of UGT1A1 gene c.1456T>G(p.Y486D)was significantly decreased after six months of follow-up visit,but it was still higher than normal level.5.There is no evidence that UGT1A1 mutations cause liver fibrosis in childhood.