Analysis of the UGT1A1 Genotype in Hyperbilirubinemia Patients: Differences in Allele Frequency and Distribution

Objective. The spectrum of UDP-glucuronyl transferase A1 (UGT1A1) variants in hereditary unconjugated hyperbilirubinemia varies markedly between different ethnic populations. This study evaluated the UGT1A1 genotypes in hyperbilirubinemia patients from southeastern China. Methods. We enrolled 60 patients from southeastern China (44 men and 16 women; age range: 3-76 years) with unconjugated hyperbilirubinemia and performed genetic analysis of the UGT1A1 gene by direct sequencing. Results. For patients with Gilbert syndrome, 85% (47/55) harbored pathogenic variants of UGT1A1*60. Both UGT1A1*28 and UGT1A1*81 were detected in the promoter region of UGT1A1. Additionally, 83% (20/24) of patients with Gilbert syndrome heterozygous for UGT1A1*60 had an association with heterozygous variation of UGT1A1*28 or UGT1A1*81, while 91% (21/23) of Gilbert syndrome patients homozygous for UGT1A1*60 had biallelic variations of UGT1A1*28 and UGT1A1*81. We detected 213 UGT1A1 allelic variants, including six novel variations, with the most frequent allele being the UGT1A1*60, followed by UGT1A1*28 and UGT1A1*6. All of the patients showed multiple sites of variants in UGT1A1; however, variation number was not associated with bilirubin levels (P>0.05). Conclusions. The spectrum of UGT1A1 variants in southeastern Chinese patients was distinct from other ethnic populations. Our findings broaden the knowledge concerning traits associated with UGT1A1 variants and help profile genotype-phenotype correlations in hyperbilirubinemia patients.