Gilbert's Syndrome in Children with Unconjugated Hyperbilirubinemia - An Analysis of 170 Cases

There is limited literature on Gilbert's syndrome (GS) in children with persistent unconjugated hyperbilirubinemia from Indian subcontinent. All patients (< 18 y of age) with genetically confirmed GS were included, and their profile was analysed. A total of 170 subjects were confirmed as having GS as per genetic analysis (133 with homozygous and 37 with heterozygous status). Majority were diagnosed in the adolescent age group (mean age 13.6 y). The median serum total bilirubin (TB) levels were around 3.3 mg/dl with maximum levels reaching upto 18 mg/dl. Around 15% subjects had an associated condition including hematological or hepatobiliary disease amongst others. GS is an important but under-recognised cause of unexplained unconjugated hyperbilirubinemia in Indian pediatric subjects. It may co-exist with other hematological and hepatobiliary disorders, and complicate the clinical/laboratory picture. Extent of hyperbilirubinemia may fluctuate to levels much higher than what is usually described in current world literature.

Novel mutations in Uridyl-diphosphate-glucuronosyl-transferase 1A1 (UGT1A1) gene in Tunisian patients with unconjugated hyperbilirubinemia

INTRODUCTION

Unconjugated hyperbilirubinemia (UCB) is a feature of Gilbert's syndrome (GS) and Crigler-Najjar's syndrome (CNS), which are two hereditary defects in bilirubin metabolism. Both syndromes are linked to mutations in the UGT1A1 gene, which cause either the decrease or the absence of the UGT1A1 enzymatic activity. Here, we investigated the molecular basis of the UGT1A1 gene in Tunisian patients presenting with unconjugated hyperbilirubinemia.

METHODS

Twenty-four patients with UCB were investigated. The screening protocol for hemoglobinopathies, enzymopathies, and membrane defects was executed in all patients. Afterward, the molecular analysis of the entire UGT1A1 gene was performed by DNA Sanger sequencing. Several bioinformatic tools were used to explore the effects of novel mutations.

RESULTS

Fifteen different UGT1A1 variations were identified, among which four are described here for the first time. In exon 5, the c.1412C > G; p.(Ala471Gly) and c.1589C > T; p.(Ser530Phe) mutations were detected in patients presenting with CNS type I and GS, respectively. In the 3'UTR region of UGT1A1, the c.*90C > T mutation was detected in 3 patients with CNS type I. In the same region, the c.*388C > T defect was found in a GS patient. A deleterious and damaging effect on the UGT1A1 protein were predicted for both exonic mutations. Furthermore, novel microRNAs were identified as targetting the mutated sequences for the 3'UTR mutations.

CONCLUSION

Our study provides novel data on UCB among Tunisians. Furthermore, we report four novel mutations associated with both GS and CNS. The identification of these mutations increases the spectrum of the UGT1A1 mutations and contributes to an understanding of the molecular abnormalities associated with unconjugated hyperbilirubinemia.

Homozygous Mutation on the β-Globin Polyadenylation Signal in a Tunisian Patient with β-Thalassemia Intermedia and Coinheritance of Gilbert's Syndrome

We report here the clinical, hematological and molecular data in a 50-year-old patient with β-thalassemia intermedia (β-TI) caused by a homozygous β⁺ mutation on the β-globin gene polyadenylation (polyA) signal (AATAAA>AAAAAA). β Haplotype analysis was accomplished by polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP). Haplotype and framework analysis showed that this mutation is associated with the [- - - - + + +] β haplotype and framework 1 (CCGCT) (FW1). This mutation was previously reported in the heterozygous state in association with the codon 9 (+TA) mutation in a β-TI patient originating from Tunisia. To the best of our knowledge, this is the first report describing this mutation in the homozygous state. The case reported here, coinherited Gilbert's syndrome, which is characterized by hyperbilirubinemia. This conclusion was reached by the investigation of the promoter region [A(TA)_nTAA] motif of the UGT1A1 gene, showing the (TA)₆/(TA)₇ genotype.

Clinical Significance of UGT1A1 Genetic Analysis in Chinese Neonates with Severe Hyperbilirubinemia

BACKGROUND

Neonatal hyperbilirubinemia is common in Asia, and the importance of genetically determined conditions has been recently recognized. The aim of this study was to assess the clinical utility of genetic testing in Chinese neonates with severe hyperbilirubinemia.

METHODS

Fifty-eight term infants with bilirubin level ≥ 20 mg/dL (342 μmol/L), and 65 controls were enrolled in the study. Variation status of UGT1A1, G6PD, and thalassemia genes in our study cohort was determined by direct sequencing or genotype assays.

RESULTS

Among these case infants, seven were confirmed with G6PD deficiency, four were heterozygous for α- or β-thalassemia, and forty-four were detected with at least one heterozygous UGT1A1 functional variant, including nine homozygous for UGT1A1 variation. As well as the predominant c.211G>A (Gly71Arg) variant, three UGT1A1 coding variants [c.1091C>T (Pro364Leu), c.1352C>T (pro451leu), and c.1456C>T (Tyr486Asp)] were observed in our case neonates. The results of multivariate logistic regressions, adjusted for covariates, revealed odds ratios for neonates who carried heterozygous, homozygous variation at nucleotide 211 of UGT1A1, and G6PD deficiency of 3.47 (1.26-9.55), 12.46 (1.09-142.7) ,and 12.87 (1.32-135.87) compared with those having the wild genotype and normal G6PD activity, respectively.

CONCLUSION

Besides G6PD-deficiency screening, UGT1A1 genetic analysis, and especially the UGT1A1*6(c.211G>A, p.Arg71Gly) polymorphism detection, may be taken into consideration for early diagnosis and treatment of severe hyperbilirubinemic newborns in southern China.