[Correlation between the mutation spectrum of the UGT1A1 gene and clinical phenotype in patients with inherited hyperunconjugated bilirubinemia]

Objective: To analyze the distribution characteristics of UGT1A1 mutant genes (including enhancers, promoters, and exons 1-5) and further explore the correlation between UGT1A1 genotype and clinical phenotypes in patients with inherited hyperunconjugated bilirubinemia. Methods: Patients diagnosed with hereditary hyperunconjugated bilirubinemia at Nanjing Second Hospital from June 2015 to December 2022 were retrospectively analyzed. The UGT1A1 gene was examined using Sanger sequencing in all patients. Complete blood count, liver function, and abdominal imaging examinations were performed. Comparison of categorical variable data using χ(2) testor Fisher percision tests. Comparison of continaous veriable data with normal distribution using t-test. Results: 112 cases (male:female ratio 81:31, aged 9-70 years) had inherited hyperunconjugated bilirubinemia, with a total of 14 mutation sites identified, of which seven were confirmed mutations, and the frequency ranged from high to low: (TA)n accounted for 50%, c.211G>A (p.G71R) accounted for 49.10%, 1456T>G (p.Y486D) accounted for 16.96%, c.686C>A (p.R229W) accounted for 12.5%, 1091C>T (p.P364L) accounted for 8.04%, and c- 3279T>G accounted for 0.982%. Simultaneously, all patients had one to four mutations, of which only one mutation was the most common (55.36%), followed by two mutations (37.5%), and rare three and four mutations (5.36% and 1.78%). There was no statistical significance in total bilirubin (TBil) levels among the four groups (F=0.652, P=0.583). One mutation was most common in (TA)n and c.211G>A (p.G71R), among which TA6/TA7 (n=10) and TA7/TA7 (n=14) mutations were statistically significant in TBil (t=2.143, P=0.043). The c.211G>A (p.G71R) heterozygous (n=9) and isolated (n=15) mutation had no statistical significance in TBil (t=0.382, P=0.706). The GS group accounted for 75%, the intermediate group accounted for 16.9%, and the CNS-Ⅱ group accounted for 8%. TBil was statistically significant among the three groups (F=270.992, P<0.001). There was no statistically significant difference (χ(2)=3.317, P=0.19) between mutation 1 (44 cases, 14 cases, and 4 cases, respectively) and mutations ≥ 2 (40 cases, 5 cases, and 5 cases, respectively) in the GS group, intermediate group, and CNS-II group. Conclusion: The number of UGT1A1 gene mutation sites may have no synergistic effect on TBil levels in patients with inherited hyperunconjugated bilirubinemia. TA7/TA7 mutations are not uncommon, and TBil levels are relatively high.

Case report: A rare case of pyruvate kinase deficiency and Crigler-Najjar syndrome type II with a novel pathogenic variant of PKLR and UGT1A1 mutation

Pyruvate Kinase Deficiency (PKD) and Crigler-Najjar syndrome are rare autosomal recessive liver diseases. PKD is caused by homozygous or compound heterozygous mutations in the PKLR gene, leading to non-spherocytic hereditary hemolytic anemia. On the other hand, Crigler-Najjar syndrome (CNS-II) is characterized by the loss or reduced activity of UDP-glucuronosyltransferase, resulting in elevated levels of unconjugated bilirubin, which is the primary cause of disease manifestation. To date, there have been no reported cases of patients with both conditions. In this case report, we present the unique clinical course of a 15-year-old Chinese patient with both PKD and CNS-II. The patient was admitted for evaluation of hyperbilirubinemia and exhibited yellowish skin color, icteric sclera, and splenomegaly upon physical examination. Extensive laboratory examinations ruled out viral, hemolytic, autoimmune, and inborn or acquired metabolic etiologies of liver injury. Histopathological findings indicated benign recurrent intrahepatic cholestasis (BRIC) and hemosiderosis. Surprisingly, targeted next-generation sequencing (NGS) of the patient's blood did not reveal any mutation sites associated with BRIC. Instead, it identified a novel homozygous pathogenic variant of the PKLR gene [c.1276C>T (p.Arg426Trp)] and a rare heterozygous variant of UGT1A1 gene [c.-55_-54insAT, c.1091C>T (p.Pro364Leu)]. These findings strongly suggest a diagnosis of PKD and CNS-II in the patient. Treatment with 500 mg/day of ursodeoxycholic acid proved to be effective, rapidly reducing the patient's total bilirubin levels and shortening the symptomatic period. This case highlights the importance of genetic diagnosis in accurately identifying the underlying cause of hyperbilirubinemia, especially in patients with rare hereditary diseases. Furthermore, NGS can provide valuable insights into the genotype-phenotype correlation of PKD and CNS-II.

[A family study of the compound heterozygous mutation of the UGT1A1 gene causing Crigler-Najjar syndrome type II]

Objective: To investigate the family gene features in Crigler-Najjar syndrome (CNS) type II. Methods: The UGT1A1 gene and related bilirubin metabolism genes were comprehensively analysed in a CNS-II family (3 CNS-II, 1 Gilbert syndrome, and 8 normal subjects). The genetics basis of CNS-II were investigated from the perspective of family analysis. Results: In three cases, compound heterozygous mutations at three sites of the UGT1A1 gene (c.-3279T > G, c.211G > A and c.1456T > G) caused CNS-II. Gilbert syndrome and CNS-II were not significantly associated with distribution or diversity loci. Conclusion: The compound heterozygous pathogenic mutations (c.-3279T > G, c.211G > A, and c.1456T > G) at three loci of the UGT1A1 gene may be the feature of the newly discovered CNS-II family genes based on the CNS-II family study.

Genetic testing of UGT1A1 in the diagnosis of Gilbert syndrome: The discovery of seven novel variants in the Chinese population

BACKGROUND

Genetic testing of UGT1A1 was used to facilitate the diagnosis of Gilbert syndrome, and analyze the distribution features of pathogenic variants in the Chinese population.

METHODS

DNA was extracted from whole blood samples of patients with unconjugated hyperbilirubinemia, and sequencing of the UGT1A1 gene was performed after PCR amplification. After alignment with reference sequences, the known pathogenic variants were identified, the variant spectrum was analyzed, and the pathogenicity of novel variants was predicted using online mutation prediction tools.

RESULTS

A total of 117 patients were confirmed with Gilbert syndrome by UGT1A1 genetic diagnosis, where the most common pathogenic variants included promoter A(TA)₇ TAA insertion and p.Gly71Arg missense variant. Following novel variants were also identified: p.Ala61Gly, p.Tyr67Phe, p.Leu166Alafs*16, p.Arg240Lys, p.Ser306Phe, p.Arg341Gln, and p.Glu424* variants.

CONCLUSIONS

Genetic testing of UGT1A1 in clinical practices could facilitate confirming Gilbert syndrome and performing differential diagnosis. The pathogenic variant spectrum in the Chinese population was similar to other Asian populations. The novel pathogenic variants identified in this study require further investigation.

Management of Crigler-Najjar syndrome

Crigler-Najjar syndrome is a rare autosomal recessive inherited non-hemolytic unconjugated hyperbilirubinemia caused by UDP-glucuronosyltransferase deficiency. There are two forms of this disorder. Type 1 disease is associated with severe jaundice and neurologic impairment due to bilirubin encephalopathy that can result in permanent neurologic sequelae. Type 2 disease is associated with a lower serum bilirubin concentration and affected patients survive into adulthood without neurologic impairment. Currently, liver transplantation is the only available therapeutic method for these patients. Developing new curative approaches is a clinical need.

Outcome of liver transplantation and prevalence of liver fibrosis in Crigler-Najjar syndrome

INTRODUCTION

Crigler-Najjar syndrome (CNS) is a rare inherited disorder that is characterized by high levels of non-hemolytic, unconjugated hyperbilirubinemia leading to brain damage and even death. Liver transplantation (LT) can correct the metabolic defect, but there are little data regarding LT in this patient cohort. The liver parenchyma has been considered to be structurally normal in CNS, but there is growing evidence of clinically silent but histologically significant fibrosis in CNS patients.

PATIENTS AND METHODS

We included 13 patients in our retrospective study who underwent LT at our center. Patient survival, graft function, and long-term complications were evaluated over a median follow-up period of 10 years (range: 1-16 years). In addition, the prevalence of histologically relevant fibrosis was characterized.

RESULTS

The overall survival among our LT patients was 100%. The graft survival was only 61.5%. During the follow-up period, 5 LT patients had to undergo retransplantation. More than 45% of our patients showed histological signs of fibrosis.

CONCLUSION

LT remains the only definite therapeutic option for severe CNS but needs to be considered thoroughly regarding the clinical risk-benefit-ratio and impact on quality of life. Furthermore, hepatic parenchymal injury needs to be considered while evaluating future therapeutic options for CNS.

[Analysis of mutation site characteristics of Gilbert syndrome and Crigler--Najjar syndrome in relation to uridine diphosphate glucuronosyltransferase A1 gene]

Objective: To investigate the mutation characteristics and clinical relevance of Gilbert syndrome (GS) and Crigler-Najjar syndrome (CNS) in relation to uridine diphosphate glucuronosyltransferase A1 (UGT1A1) gene. Methods: The characteristics of UGT1A1 gene mutation and their clinical relevance were analyzed by searching PubMed and Human Gene Mutation Databases. Results: A total of 163 mutation sites were found in the UGT1A1 gene since November 16, 2018. The following patterns existed at the above sites: (1) the numbers of gene mutations occurring between different exons of UGT1A1 was related to GS or CNS phenotypes, and were positively correlated with the length of the exon; (2) nonsense point mutations was mainly occurred in type I of CNS; (3) GS, Crigler-Najjar syndrome type II compound heterozygous mutation sites had a certain combination and distribution, among which - 3279t > G mutation was found in all four GS complex heterozygous compositions; (4) UGT1A1 gene mutation sites reported in Asia had marked aggregation in c.211-c.558. Conclusion: UGT1A1 gene mutation characteristics and clinical relevance varies with different mutation sites, reporting areas and populations. This study has reference value for basic research and clinical diagnosis and treatment of GS and CNS.

A Quantitative In Vitro Potency Assay for Adeno-Associated Virus Vectors Encoding for the UGT1A1 Transgene

Potency assessment of clinical-grade vector lots is crucial to support adeno-associated virus (AAV) vector release and is required for future marketing authorization. We have developed and validated a cell-based, quantitative potency assay that detects both transgenic expression and activity of an AAV8-hUGT1A1 vector, which is currently under clinical evaluation for the treatment of Crigler-Najjar syndrome. Potency of AAV8-hUGT1A1 was evaluated in vitro. After transduction of human hepatoma 7 (Huh7) cells, transgene-positive cells were quantified using flow cytometry and transgenic activity by a bilirubin conjugation assay. The in vitro potency of various AAV8-hUGT1A1 batches was compared with their potency in vivo. After AAV8-hUGT1A1 transduction, quantification of UGT1A1-expressing cells shows a linear dose-response relation (R² = 0.98) with adequate intra-assay and inter-day reproducibility (coefficient of variation [CV] = 11.0% and 22.6%, respectively). In accordance, bilirubin conjugation shows a linear dose-response relation (R² = 0.99) with adequate intra- and inter-day reproducibility in the low dose range (CV = 15.7% and 19.7%, respectively). Both in vitro potency assays reliably translate to in vivo efficacy of AAV8-hUGT1A1 vector lots. The described cell-based potency assay for AAV8-hUGT1A1 adequately determines transgenic UGT1A1 expression and activity, which is consistent with in vivo efficacy. This novel approach is suited for the determination of vector lot potency to support clinical-grade vector release.

A case report of a novel 22 bp duplication within exon 1 of the UGT1A1 in a Sudanese infant with Crigler-Najjar syndrome type I

Background

Crigler Najjar type 1 is a rare autosomal recessive condition caused by the absence of UDPGT enzyme due to mutations in the UGT1A1 gene. This enzyme is responsible for elimination of unconjugated bilirubin from the body by glucuronidation. Affected individuals are at risk for kernicterus and require lifelong phototherapy. Liver transplant is the only definitive treatment.

Case presentation

Here we report a case of a 6 month old Sudanese female infant with CN1 whose molecular analysis revealed a novel homozygous 22 base pair duplication (c.55_76dup) in the coding exon 1 of the UGT1A1 gene. This 22 bp duplication causes a frame shift leading to a premature stop codon. She underwent a successful liver transplant at 7 months of age and is doing well at 1 year follow-up.

Conclusion

This study shows that molecular diagnosis helps in precise diagnosis of CN1 and in prognosis, prompt medical intervention and appropriate therapy. This particular 22 bp duplication within the coding region of UGT1A1 can be a founder mutation in the Sudanese population.

A novel UGT1A1 gene mutation causing severe unconjugated hyperbilirubinemia: a case report

BACKGROUND

Crigler-Najjar syndrome (CNs) presents as unconjugated hyperbilirubinemia, as a result of UGT1A1 deficiency, and can be categorized in a severe (type I) and mild (type II) phenotype. CNs type II patients usually benefit from phenobarbital treatment that induces residual UGT1A1 activity.

CASE PRESENTATION

Here we present a CNs type II patient that is not responsive to phenobarbital treatment, which can be explained by two heterozygous mutations in the UGT1A1 gene. A 3 nucleotide insertion in the HNF-1α binding site in the proximal promoter previously reported in a Crigler-Najjar patient on one allele and a novel two nucleotide deletion in exon 1, resulting in a frameshift and a premature stop codon.

CONCLUSION

In newly diagnosed CNs patients with unconjugated bilirubin levels consistent with CNs type II but that are unresponsive to phenobarbital treatment, disruption of the HNF-1α binding site in the proximal promoter should be considered as a probable cause. Upon confirming a mutation in the HNF-1α site, phenobarbital treatment should be stopped or at least be reconsidered because of its sedative effects and its teratogenic properties.

Preclinical Development of an AAV8-hUGT1A1 Vector for the Treatment of Crigler-Najjar Syndrome

Adeno-associated viruses (AAVs) are among the most efficient vectors for liver gene therapy. Results obtained in the first hemophilia clinical trials demonstrated the long-term efficacy of this approach in humans, showing efficient targeting of hepatocytes with both self-complementary (sc) and single-stranded (ss) AAV vectors. However, to support clinical development of AAV-based gene therapies, efficient and scalable production processes are needed. In an effort to translate to the clinic an approach of AAV-mediated liver gene transfer to treat Crigler-Najjar (CN) syndrome, we developed an (ss)AAV8 vector carrying the human UDP-glucuronosyltransferase family 1-member A1 (hUGT1A1) transgene under the control of a liver-specific promoter. We compared our construct with similar (sc)AAV8 vectors expressing hUGT1A1, showing comparable potency in vitro and in vivo. Conversely, (ss)AAV8-hUGT1A1 vectors showed superior yields and product homogeneity compared with their (sc) counterpart. We then focused our efforts in the scale-up of a manufacturing process of the clinical product (ss)AAV8-hUGT1A1 based on the triple transfection of HEK293 cells grown in suspension. Large-scale production of this vector had characteristics identical to those of small-scale vectors produced in adherent cells. Preclinical studies in animal models of the disease and a good laboratory practice (GLP) toxicology-biodistribution study were also conducted using large-scale preparations of vectors. These studies demonstrated long-term safety and efficacy of gene transfer with (ss)AAV8-hUGT1A1 in relevant animal models of the disease, thus supporting the clinical translation of this gene therapy approach for the treatment of CN syndrome.

[Study on spectrum of UGT1A1 mutations in connection with inherited non-hemolytic unconjugated hyperbilirubinemia]

Objective: To compare and analyze patient's general condition, changes in laboratory parameters, and the spectrum of UGT1A1 mutations in patients with inherited non-hemolytic unconjugated hyperbilirubinemia. Methods: A retrospective study was conducted at Nanjing Second Hospital from January 2015 to July 2018 and patients' demographic characteristics, liver function test, and UGT1A1 gene were analyzed. The categorical variable data were compared by χ (2) test. The normal distribution continuous variable data were compared by t-test and the non-normal distribution continuous variable data were compared using Mann-Whitney U test. Results: Of the 51 patients with inherited non-hemolytic unconjugated hyperbilirubinemia, 44 (86.3%) were Gilbert's syndrome (GS) and seven (13.7%) were Crigler-Najjar syndrome type II (CNS- II). The male to female ratio was 2.9:1 and the average age was 36.11 ± 13.17 years. Six variant types were detected: C. -40_-39insTA, C. -3279T > G, c.211G > A (p.G71R), c.686C > A (p.P229Q), c.1091C > T (p.P364L), c.1456T > G (P.Y486D). Among them, c.211G > A accounted for 58.82% (30/51), c.-40_-39insTA accounted for 27.5% (14/51), and c.1456T > G accounted for 25.5% (13/51). The total bilirubin(TB) and unconjugated bilirubin (UCB) in CNS-II patients were significantly higher than GS patients[155.91 (130 ~ 207) vs. 38.25(29 ~ 52.15) μmol/L, U = 0, P < 0.01; 144.13 (120.8 ~ 197) vs. 30.00 (21.7 ~ 46.75) μmol/L, U = 0.00, P < 0.01, respectively]. Exon mutations of c.1091C > T and c.1456T > G were statistically significant(P < 0.01).There were no differences in age, TB, UCB, alanine aminotransferase (ALT) and aspartate aminotransferase (AST) between the c.211G > A homozygous variants and heterozygous variants (P > 0.05). Conclusion: The common pathogenic mutations of UGT1A1 gene were c.211G > A, c.-40_-39insTA, c.1456T > G. c.211G > A. The mutation has little effect on the level of total bilirubin, but c.1091C > T, c.1456T > G mutations has great influence on the level of total bilirubin.

Diagnostic criteria and contributors to Gilbert's syndrome

Hyperbilirubinemia is a well-known condition in the clinical setting; however, the causes of elevated serum bilirubin are diverse, as are the clinical ramifications of this condition. For example, diagnoses of individuals vary depending on whether they exhibit an unconjugated or conjugated hyperbilirubinemia. Diagnoses can include conditions of disordered bilirubin metabolism (Gilbert's, Crigler-Najjar, Rotor, or Dubin-Johnson syndromes) or an acquired disease, including alcoholic/non-alcoholic fatty liver disease, hepatotropic hepatitis, cirrhosis, or hepato-biliary malignancy. Assessment of bilirubin concentrations is typically conducted as part of routine liver function testing. Mildly elevated total bilirubin with normal serum activities of liver transaminases, biliary damage markers, and red blood cell counts, however, may indicate the presence of Gilbert's syndrome (GS), a benign condition that is present in ∼5-10% of the population. In this case, mildly elevated unconjugated bilirubin in GS is strongly associated with "reduced" prevalence of chronic diseases, particularly cardiovascular diseases (CVD) and type 2 diabetes mellitus (and associated risk factors), as well as CVD-related and all-cause mortality. These reports challenge the dogma that bilirubin is simply a potentially neurotoxic by-product of heme catabolism and emphasize the importance of understanding its potential beneficial physiologic and detrimental pathophysiologic effects, in order to appropriately consider bilirubin test results within the clinical laboratory setting. With this information, we hope to improve the understanding of disorders of bilirubin metabolism, emphasize the diagnostic importance of these conditions, and outline the potential impact GS may have on resistance to disease.

Inflammatory signature of cerebellar neurodegeneration during neonatal hyperbilirubinemia in Ugt1 -/- mouse model

Background

Severe hyperbilirubinemia is toxic during central nervous system development. Prolonged and uncontrolled high levels of unconjugated bilirubin lead to bilirubin-induced neurological damage and eventually death by kernicterus. Bilirubin neurotoxicity is characterized by a wide array of neurological deficits, including irreversible abnormalities in motor, sensitive and cognitive functions, due to bilirubin accumulation in the brain. Despite the abundant literature documenting the in vitro and in vivo toxic effects of bilirubin, it is unclear which molecular and cellular events actually characterize bilirubin-induced neurodegeneration in vivo.

Methods

We used a mouse model of neonatal hyperbilirubinemia to temporally and spatially define the response of the developing cerebellum to the bilirubin insult.

Results

We showed that the exposure of developing cerebellum to sustained bilirubin levels induces the activation of oxidative stress, ER stress and inflammatory markers at the early stages of the disease onset. In particular, we identified TNFα and NFKβ as key mediators of bilirubin-induced inflammatory response. Moreover, we reported that M1 type microglia is increasingly activated during disease progression.

Failure to counteract this overwhelming stress condition resulted in the induction of the apoptotic pathway and the generation of the glial scar. Finally, bilirubin induced the autophagy pathway in the stages preceding death of the animals.

Conclusions

This study demonstrates that inflammation is a key contributor to bilirubin damage that cooperates with ER stress in the onset of neurotoxicity. Pharmacological modulation of the inflammatory pathway may be a potential intervention target to ameliorate neonatal lethality in Ugt1^-/- mice.

Electronic supplementary material

The online version of this article (doi:10.1186/s12974-017-0838-1) contains supplementary material, which is available to authorized users.

John's Wort) in a patient with Crigler-Najjar syndrome type II

AIMS

Crigler-Najjar syndrome (CN) type II is a congenital disease with unconjugated hyperbilirubinemia due to a deficiency of uridine 5'-diphospho-glucuronosyltransferase 1A1. Since the currently proposed treatment with phenobarbital is associated with adverse reactions, we investigated the effect of hypericum extract.

METHODS

Repetitive determination of total serum bilirubin in a female with CN type II before, during and after daily treatment with 900 mg hypericum extract on two occasions for 8 weeks. Confirmation of the enzyme-inducing effect of hypericum using the cytochrome P450 3A4 probe drug i.v. midazolam.

RESULTS

Hypericum reduced midazolam exposure by 42% and the total serum bilirubin concentration by 30 to 35%.

CONCLUSIONS

Hypericum extract is a potential alternative to phenobarbital in patients with CN type II.

Disruption of HNF1α binding site causes inherited severe unconjugated hyperbilirubinemia

Crigler-Najjar syndrome presents as severe unconjugated hyperbilirubinemia and is characteristically caused by a mutation in the UGT1A1 gene, encoding the enzyme responsible for bilirubin glucuronidation. Here we present a patient with Crigler-Najjar syndrome with a completely normal UGT1A1 coding region. Instead, a homozygous 3 nucleotide insertion in the UGT1A1 promoter was identified that interrupts the HNF1α binding site. This mutation results in almost complete abolishment of UGT1A1 promoter activity and prevents the induction of UGT1A1 expression by the liver nuclear receptors CAR and PXR, explaining the lack of a phenobarbital response in this patient. Although animal studies have revealed the importance of HNF1α for normal liver function, this case provides the first clinical proof that mutations in its binding site indeed result in severe liver pathology stressing the importance of promoter sequence analysis.

Molecular Analysis of the UGT1A1 Gene in Korean Patients with Crigler-Najjar Syndrome Type II

PURPOSE

Crigler-Najjar syndrome type II (CN-2) is characterized by moderate non-hemolytic unconjugated hyperbilirubinemia as a result of severe deficiency of bilirubin uridine diphosphate-glucuronosyltransferase (UGT1A1). The study investigated the mutation spectrum of UGT1A1 gene in Korean children with CN-2.

METHODS

Five Korean CN-2 patients from five unrelated families and 50 healthy controls were enrolled. All five exons and flanking introns of the UGT1A1 gene were amplified by polymerase chain reaction (PCR) and the PCR products were directly sequenced.

RESULTS

All children initially presented with neonatal jaundice and had persistent indirect hyperbilirubinemia. Homozygous p.Y486D was identified in all five patients. Three patients had an associated homozygous p.G71R and two a heterozygous p.G71R. The allele frequency of p.Y486D and p.G71R in healthy controls was 0 and 0.16, respectively. No significant difference in mean serum bilirubin levels was found between homozygous carriers of p.G71R and heterozygous carriers.

CONCLUSION

The combination of homozygous p.Y486D and homozygous or heterozygous p.G71R is identified. The p.Y486D and p.G71R can be screened for the mutation analysis of UGT1A1 in Korean CN-2 patients.

Mutation Analysis in Crigler-Najjar Syndrome Type II-Case Report and Literature Review

Crigler-Najjar syndrome (CN) is a congenital defect in bilirubin conjugation due to complete or partial deficiency of uridine 5'-diphosphate-glucuronosyltransferase (UGT). It is of two types: CN type I and CN type II. Patients with CN type II present with indirect hyperbilirubinemia in adulthood. We report a CN type II with homozygous mutation in UGT1A1 gene. This is the first case report of mutation analysis in CN type II from India.

Auxiliary liver transplantation: a form of gene therapy in selective metabolic disorders

Auxiliary liver transplantation is an accepted form of therapy in acute liver failure and in certain metabolic disorders. We report India's first successful auxiliary liver transplantation for Crigler-Najjar syndrome type 1, showing that it is technically feasible and safe procedure. It is utmost important to select appropriate cases for auxiliary transplant for successful long-term outcome. The surgeon should also have an understanding of the portal flow dynamics, as steal phenomenon can occur, depriving blood blow to either graft or native liver. Though successful in animal models, gene therapy is still in experimental stage in humans and pace of progress has been disappointing. Auxiliary liver transplantation retains the native liver for future gene therapy. These children are young and are likely to have a long life expectancy, and withdrawal of immunosuppression would be a huge advantage.