Clinical characteristics and follow-up of a newborn with Dubin-Johnson Syndrome: A clinical case report.

BACKGROUND: Dubin-Johnson syndrome (DJS) is a rare autosomal recessive liver disorder, characterized by conjugated hyperbilirubinemia. This case report investigates the clinical characteristics and longitudinal outcomes of a neonate diagnosed with DJS. METHODS: A newborn presented with elevated bilirubin levels and abnormal liver enzyme readings. Comprehensive genetic evaluation was conducted, which included peripheral blood sample collection from the infant and both parents after obtaining informed consent and high-throughput trio exome sequencing was performed. The genetic analysis revealed 2 significant mutations in the ABCC2 gene on chromosome 10: the insertion mutation c.4237(exon30)_c.4238(exon30)ins CT, inherited from the father, and the missense mutation c.517(exon5)G > A, inherited from the mother. Both mutations were classified as pathogenic according to the ACMG 2015 guidelines, indicating a compound heterozygous inheritance pattern. The patient's treatment regimen included phototherapy, which was initiated to address her jaundice upon admission. To support liver function and regulate gut activity, oral ursodeoxycholic acid (20 mg/kg/dose, twice a day) and probiotics were administered. Additionally, a postdischarge medication plan involving a low-dose regimen of phenobarbital (3.5 mg/kg/dose, twice a day) was implemented for 2 weeks. RESULTS: During a 2-year follow-up after discharge, the infant's bilirubin levels significantly decreased, and liver enzymes, including GGT, progressively normalized. CONCLUSION: This case report enhances the understanding of DJS in neonates by emphasizing the clinical ramifications of compound heterozygous mutations within the ABCC2 gene and documenting the evolution of the disease. The gradual normalization of liver function tests suggests potential compensatory mechanisms in response to the genetic abnormalities in neonates with DJS. The correlation between the patient's genetic profile of compound heterozygosity and her milder clinical phenotype warrants attention, suggesting that this specific genetic configuration may be associated with less severe manifestations of the disease. The necessity for long-term follow-up is highlighted, recognizing that intercurrent stress conditions could influence the hepatic profile and potentially exacerbate symptoms. Such sustained observation is crucial to further delineate the genomic and clinical landscape of DJS, offering opportunities to refine prognostic and therapeutic approaches.

Excessive vincristine exposure in a child being treated for acute lymphoblastic leukaemia with underlying Dubin-Johnson syndrome: a case report.

BACKGROUND: Dubin-Johnson syndrome is a rare benign autosomal recessive condition that causes an isolated increase of conjugated bilirubin in the serum. Impaired biliary excretion is due to mutation in the multiple drug-resistance protein 2 gene (MRP2). CASE PRESENTATION: We describe the case of a 4-year-old girl being treated for acute lymphoblastic leukaemia who had a history of conjugated hyperbilirubinaemia and persistently elevated bilirubin levels on initiation of chemotherapy. During treatment for leukaemia, she was diagnosed with Dubin-Johnson syndrome for the underlying condition. Following administration of vincristine at the recommended dose of 1.5 mg/m2, an abnormally high vincristine exposure was observed (AUC > 200 µg/L*h), approximately 3 times higher than previously reported exposures in a comparable clinical setting. Vincristine dose reductions were applied on subsequent cycles of treatment and resulted in markedly reduced drug exposures, within the normal target range. CONCLUSION: This case provided a rare opportunity to assess the impact of MRP2 mutations associated with Dubin-Johnson syndrome on the pharmacokinetics of vincristine and strongly indicates that a marked dose reduction should be recommended. Clinicians should be made aware of the potential for altered drug disposition for agents such as vincristine in patients with this rare genetic condition.

Urinary coproporphyrins as a diagnostic biomarker of Dubin-Johnson syndrome in neonates: A diagnostic pathway is proposed.

Background: Dubin-Johnson syndrome (DJS) presents during the neonatal period with a phenotype that overlaps with a broad list of causes of neonatal cholestasis (NC), which makes the identification of DJS challenging for clinicians. We conducted a case-controlled study to investigate the utility of urinary coproporphyrins (UCP) I% as a potential diagnostic biomarker. Methods: We reviewed our database of 533 cases of NC and identified 28 neonates with disease-causing variants in ATP-binding cassette-subfamily C member 2 (ABCC2) gene "Cases" (Study period 2008-2019). Another 20 neonates with cholestasis due to non-DJS diagnoses were included as "controls." Both groups underwent UCP analysis to measure CP isomer I percentage (%). Results: Serum alanine aminotransferase (ALT) levels were within the normal range in 26 patients (92%) and mildly elevated in 2 patients. ALT levels were significantly lower in neonates with DJS than in NC from other causes (P < 0.001). The use of normal serum ALT levels to predict DJS among neonates with cholestasis had a sensitivity of 93%, specificity 90%, positive predictive value (PPV) 34%, and negative predictive value (NPV) 99.5%. The median UCPI% was significantly higher in DJS patients [88%, interquartile range (IQR) 1-IQR3, 84.2%-92.7%] than in NC from other causes [67%, (IQR1-IQR3, 61%-71.5%; Confidence interval 0.18-0.28; P< 0.001)]. The use of UCPI% >80% to predict DJS had a sensitivity, specificity, PPV, and NPV of 100%. Conclusion: Based on the results from our study, we propose sequencing of the ABCC2 gene in neonates with normal ALT, presence of cholestasis and UCP1% >80%.

Concurrence of novel mutations causing Gilbert's and Dubin-Johnson syndrome with poor clinical outcomes in a Han Chinese family.

Dual-hereditary jaundice (Dubin-Johnson syndrome (DJS) and Gilbert's syndrome (GS)) is a rare clinical entity resulting from defects of the ATP binding cassette subfamily C member 2 (ABCC2) and UDP glucuronosyltransferase family 1 member A1 (UGT1A1) genes with autosomal recessive inheritance. In this study, we aimed to investigate the mutation profiles and characterize the phenotypes in a Han Chinese family with DJS and GS. Genetic screening for variants in the ABCC2 and UGT1A1, immunohistochemistry for expression of ABCC2, and histopathological examination were carried out. The proband and his brother had unconjugated and conjugated hyperbilirubinemia after birth. The proband's sister had only conjugated hyperbilirubinemia after birth. The proband developed into pleural effusions and ascites, pericardial thickening, intrahepatic and extrahepatic biliary duct dilatation, and enlarged gallbladder at age 50. Hepatocellular carcinoma occurred in the proband's brother at age 46. Seven compound defects of the ABCC2 gene [c.2414delG, p.(Ile1489Gly), p.(Thr1490Pro), and p.(Ile1491Gln)] and the UGT1A1 gene (c.-3279T>G, p.(Gly71Arg), and p.(Pro451Leu)) were identified in family members. Accumulation of pigment in hepatocytes characteristic of that in DJS was present in the proband and his brother. Expression of ABCC2 protein was markedly diminished in the patient's liver. Our results show a different genetic profile of DJS and GS in a Han Chinese family, indicating a more complex pattern of dual-hereditary jaundice among different populations. The present study illuminates the underpinnings of DJS and GS and extends the mutation profiles and phenotypes of these two syndromes in dual-hereditary jaundice.

Genotype-Phenotype Association in ABCC2 Exon 18 Missense Mutation Leading to Dubin-Johnson Syndrome: A Case Report.

We report a case of a patient with Dubin-Johnson syndrome confirmed by a genetic study. A 50-year-old woman who had symptoms of intermittent right upper quadrant abdominal pain was diagnosed with calculous cholecystitis at another institute and was presented to our hospital for a cholecystectomy. She had no history of liver disease, and her physical examination was normal. Abdominal computed tomography showed a gallbladder stone with chronic cholecystitis. During a laparoscopic cholecystectomy for cholecystitis, a smooth, black-colored liver was noted, and a liver biopsy was performed. The biopsy specimen showed coarse, dark brown granules in centrilobular hepatocytes via hematoxylin and eosin staining. We performed a genetic study using the blood samples of the patient. In the adenosine triphosphate-binding cassette subfamily C member 2 (ABCC2) mutation study, a missense mutation in exon 18 was noted. Based on the black-colored liver without nodularity, conjugated hyperbilirubinemia, the liver biopsy results of the coarse pigment in centrilobular hepatocytes, and the ABCC2 mutation, Dubin-Johnson syndrome was diagnosed. The patient was managed with conservative care using hepatotonics. One month after follow-up, total bilirubin and direct bilirubin remained in a similar range. Another follow-up was planned a month later, and the patient maintained her use of hepatotonics.

[The phenotypes and genotypes of four patients with Dubin-Johnson syndrome].

OBJECTIVE: To explore the genetic etiology in four patients with hyperbilirubinemia, and discuss the correlation between clinical characteristics and molecular basis. METHODS: The data of clinical manifestation and auxiliary examinations were collected. Genomic DNA of the four patients was extracted and analyzed by next-generation sequencing using the panel including genes involved in hereditary metabolic liver diseases. Suspected variants were verified by Sanger sequencing. RESULTS: All of the four patients were males with normal liver enzymes. It was revealed that all the patients had heterozygous variants, among which c.3011C>T, c.2443C>T and c.2556del were the variants which have not been reported previously. CONCLUSION: All of the patients were diagnosed as Dubin-Johnson syndrome (DJS) caused by ABCC2 gene variants. The novel variants add to the spectrum of genetic variants of the disease. Because of the favorite prognosis, precise diagnosis can greatly reduce the psychological pressure of patients and avoid excessive treatments. At the same time, it could provide pertinent genetic counseling for the families.

[Genetic analysis of a case with Dubin-Johnson syndrome due to two novel variants of ABCC2 gene].

OBJECTIVE: To explore the genetic etiology and differential diagnosis for a patient with jaundice. METHODS: Clinical data of the patient and his parents were collected. Genes associated with metabolic liver diseases were subjected to high-throughput sequencing. The pathogenicity of the candidate variants was predicted by using bioinformatics software. RESULTS: High-throughput sequencing revealed that the proband has harbored two variants of the ABCC2 gene (NM_000392) including c.3011C>T (p.T1004I) and c.3541C>T (p.R1181X), which were respectively inherited from his father and mother. Both variants have been previously unreported and predicted to be pathogenic by bioinformatics analysis. CONCLUSION: The proband was diagnosed with Dubin-Johnson syndrome due to the compound heterozygous variants of the ABCC2 gene. Genetic testing has enabled accurate differential diagnosis of Dubin-Johnson syndrome in this patient.

Benign inheritable disorders of bilirubin metabolism manifested by conjugated hyperbilirubinemia-A narrative review.

Bilirubin, a breakdown product of heme, is normally glucuronidated and excreted by the liver into bile. Failure of this system can lead to a buildup of conjugated bilirubin in the blood, resulting in jaundice. Hyperbilirubinemia is an important clinical sign that needs to be investigated under a stepwise evaluation. Inherited non-hemolytic conjugated hyperbilirubinemic conditions include Dubin-Johnson syndrome (caused by mutations affecting ABCC2 gene) and Rotor syndrome (caused by the simultaneous presence of mutations in SLCO1B1 and SLCO1B3 genes). Although classically viewed as benign conditions requiring no treatment, they lately gained an increased interest since recent studies suggested that mutations in the responsible genes leading to hyperbilirubinemia, as well as minor genetic variants, may result in an increased susceptibility to drug toxicity. This article provides a comprehensive review on the pathophysiology of Dubin-Johnson and Rotor syndromes, presenting the current knowledge concerning the molecular details and basis of these conditions.

In silico screening and analysis of single-nucleotide polymorphic variants of the ABCC2 gene affecting Dubin-Johnson syndrome.

BACKGROUND AND STUDY AIMS: Dubin-Johnson syndrome (DJS) is a benevolent genetic disorder of the liver with autosomal inheritance. It is a rare disorder characterized by an increase in conjugated bilirubin and anomaly in coproporphyrin clearance. DJS is caused by deleterious mutations in the ABCC2 gene. A polymorphism in the ABCC2 gene causes malfunctions in its ability to regulate the efflux of different organic anions, such as bilirubin, from hepatocytes to the canaliculi. Multidrug resistance protein 2 (MRP2) encoded by the ABCC2 gene is one of the main regulators of the export of bilirubin to respective sites. ABCC2 gene mutations have widely drawn attention in the pathology of DJS in various populations. PATIENTS AND METHODS: The ABCC2 gene was subjected to the National Center for Biotechnology Information (NCBI) database in 2020, and non-synonymous single-nucleotide polymorphisms (nsSNPs) and variants in untranslated regions were studied using different computational servers. SIFT, Protein variation effect analyzer, and PolyPhen-2 were used to retrieve the damaging Single-nucleotide polymorphisms (SNPs); PhD-SNP, SNPs&GO, and Protein Analysis Through Evolutionary Relationships were used to predict the association of nsSNPs with DJS; Mutation3D illustrated the location of variants in the protein; SNAP2, MutPred2, ELASPIC, and HOPE were used to predict the structural and functional effects of these mutations on MRP2; and I-mutant 3.0 and MuPro were used to determine the effects of polymorphism on the function of MRP2. RESULTS: In this study, 18,947 SNPs were screened from the NCBI database, followed by a series of refinement of variants using online available servers. We concluded that 41 ABCC2 gene variants are vital etiological candidates for DJS in humans. These 41 variants had highly damaging effects on the MRP2 protein, which may lead to deficient transportation capacity, thereby affecting the efflux of bilirubin across the canalicular membrane. CONCLUSION: In silico tools are an alternative approach for predicting the target SNPs. Hence, previously unreported variants can be considered strong etiological candidates for diseases related to MRP2.

Clinical characteristics and liver profiles of Dubin-Johnson syndrome in neonates: Multicenter retrospective study.

OBJECTIVES: Dubin-Johnson syndrome (DJS) is a rare benign autosomal recessive disorder characterized by cholestasis in neonates. The aim of the present study was to describe the clinical characteristics, hepatic profiles, histopathology, gene mutations, and treatment outcomes of neonatal DJS. MATERIAL AND METHODS: A multicenter retrospective study was undertaken with patients who had DJS. The authors identified DJS in neonates and reviewed medical records for details. The diagnosis of DJS was based on the presence of unexplained prolonged conjugated hyperbilirubinemia and presence of a mutation in the ATP Binding Cassette Subfamily C Member 2 (ABCC2) gene detected in genomic DNA extracted from circulating blood cells. RESULTS: Eleven children with DJS were identified in the study. The study population comprised eight males and three females. The median age at presentation was 21 days. Dysmorphic features were not recorded in any of the patients. Cholestasis, high serum bile acids, and normal transaminase levels were found in all patients (100%). Serum alkaline phosphatase and gamma glutamyl transferase were elevated in four patients (36%). Hypoalbuminemia and coagulopathy were not noted in these patients. Consanguinity was present in nine patients (82%). All patients had normal abdominal ultrasound findings. Genetic molecular testing showed that 82% of the patients reported a pathogenic variant of the ABCC2 gene defect with the same variant c.2273G>T (Gly 758 val) chromosome 10. All patients were alive without liver transplantation. CONCLUSIONS: This is the largest study worldwide describing that neonatal DJS is a benign cholestatic disease with favorable outcomes. Low-grade direct hyperbilirubinemia, normal transaminases, and elevated serum bile acids are the main characteristic findings of DJS.

Neonatal Dubin-Johnson syndrome: biochemical parameters, characteristics, and genetic variants study.

BACKGROUND: The clinical characteristics and gene mutation characteristics of children with Dubin-Johnson syndrome (DJS) need in-depth study. METHODS: The clinical and genomic data of neonatal Dubin-Johnson syndrome (NDJS) and 155 cases with idiopathic cholestasis (IC) were analyzed from June 2016 to August 2020 RESULTS: ABCC2 gene variants were identified in eight patients, including one patient with homozygous variants and seven patients with compound heterozygous variants. A total of 13 different ABCC variants were detected in the NDJS patients, including three nonsense variants, six missense variants, three frameshift variants, and a splice site variant. The variant c.2443C > T (p.R815X), c.4237_4238insCT (p.H1414Lfs*17), c.960_961insGT (p.L322Cfs*3), c.4250delC (p.S1417Ffs*14), c.2224G > A (p.D742N), c.4020G > C (p.K1340N), and c.2439 + 5G > A were not reported in the Human Gene Variant Database. There was no significance in the sex, birth weight, and onset age between the NDJS and IC groups. Compared with the IC group, the NDJS group had significantly higher levels of total bilirubin (TB), but a significantly lower level of alanine transaminase and a ratio of direct bilirubin (DB) to TB. There is no significance in total bile acid, gamma-glutamyl-transpeptidase, albumin, or international normalized ratio between the two groups. CONCLUSIONS: NDJS should be considered in prolonged neonatal intrahepatic cholestasis, especially in infants with normal or slightly elevated transaminase levels. IMPACT: Explore the biochemical parameters, characteristics, and genetic profile of NDJS. By summarizing the characteristics of biochemical indicators, seven new mutation types of the ABCC2 gene were detected, which expanded the mutation spectrum of the ABCC2 gene. NDJS should be considered in prolonged neonatal intrahepatic cholestasis, especially in infants with normal or slightly elevated transaminase levels.

[Clinical and pathological features of Dubin-Johnson syndrome].

Objective: To explore the clinical and pathological features of Dubin-Johnson syndrome. Methods: The clinical and pathological characteristics of 18 cases of Dubin-Johnson syndrome diagnosed in the Department of Pathology of the Third Affiliated Hospital of Sun Yat-sen University from 2008 to 2018 were analyzed. Related literature was reviewed. Results: There were 15 male and three female patients. The male-to-female ratio was 5∶1. The age of the patients ranged from 17 to 73 years (median 24 years). Common clinical manifestations were jaundice, anorexia, and abnormal liver function tests. The pathological feature was the deposition of dark brown particles in the hepatocytes, especially those around the central veins. Conclusions: Dubin-Johnson syndrome mainly occurs in young people. The characteristic pathological changes are the deposition of dark brown particles in the hepatocytes around the central veins of the liver. The diagnosis of Dubin-Johnson syndrome mainly relies on clinical manifestations, laboratory examinations, histopathological examinations and genetic testing. The understanding of Dubin-Johnson syndrome can help reduce the rates of missed diagnosis and misdiagnosis of the disease.

Characterization of a novel ABCC2 mutation in infantile Dubin Johnson syndrome.

BACKGROUND AND AIMS: The Dubin Johnson Syndrome (DJS) occurs mostly in young adults but an early-onset of the disease has been reported in less common forms (Neonatal DJS and Infantile DJS). In this case, the clinical findings are of limit for the DJS diagnosis. Hence, the genetic testing remains the method of choice to provide an accurate diagnosis. In our study, we aimed to perform a genetic analysis for two siblings presented with an intrahepatic cholestasis before the age of 1 year to provide a molecular explanation for the developed phenotype. PATIENTS & METHODS: A Tunisian family, having two siblings, manifesting signs of a hepatopathy, was enrolled in our study. A molecular analysis was performed, using a panel-based next generation sequencing, supplying results that were the subject of computational analysis. Then, a clinical follow-up was carried out to assess the evolution of the disease. RESULTS: The genetic analysis revealed the presence of a novel missense c.4179G > T, (p.M1393I) mutation in ABCC2 gene associated with a substitution c.2789G > A (R930Q) in ATP8B1 gene. Predictive results consolidated the pathogenic effect of both variants. These results confirmed the DJS diagnosis in the studied patients. The clinical course of both patients fit well with the benign nature of DJS. CONCLUSION: We described here a novel ABCC2 mutation associated with a putative ATP8B1 modifier variant. This finding constituted the first report of a complex genotype in DJS. Hence, genetic analysis by a panel-based next generation sequencing permits an accurate diagnosis and the identification of putative variants that could influence the developed phenotype.

Dubin-Johnson Syndrome as Differential Diagnosis for Neonatal Cholestasis.

OBJECTIVES: Dubin-Johnson syndrome (DJS) is an autosomal recessive disorder in which multidrug-resistance-associated protein 2 (MRP2) deficiency causes an excretion disorder of conjugated bilirubin from hepatocytes into bile canaliculi. Its clinical presentation as neonatal cholestasis (NC) is rare but represents an important differential diagnosis. We aimed to define DJS-specific characteristics in NC, in particular in contrast to biliary atresia (BA) patients, and to highlight diagnostic tools that can help to avoid invasive diagnostic tests. METHODS: We performed a review of case records from 2006 to 2020 and compared 4 DJS patients to 26 patients with proven BA consecutively diagnosed from 2014 to 2017. DJS was diagnosed by urine coproporphyrin analysis (UCA) and by genetic analysis (GA) for disease-associated ABCC2 variants. RESULTS: Four male patients with NC were diagnosed with DJS by UCA and GA. DJS patients presenting as NC showed significantly lower values for aspartate aminotransferase (AST) (P < 0.001), for alanine aminotransferase (ALT) (P = 0.002) and for gamma-glutamyl transferase (GGT) (P < 0.001) compared with BA patients. Other examinations, however, could not clearly discriminate them (e.g.: stool colour, serum bile acids, total serum bilirubin). CONCLUSIONS: DJS is not only a rare differential diagnosis in NC with a suspicious phenotype (almost normal AST, ALT) but also shows overlapping features with BA. It should, therefore, be considered in every infant with NC and an atypical liver enzyme pattern to protect patients from unnecessary, invasive examinations. For this, UCA is a fast and reliable diagnostic tool. Confirmation based on GA is recommended. DJS patients have a good long-term prognosis.

A novel homozygous frameshift variant in the ABCC2-gene in Dubin-Johnson syndrome may predispose to chronic liver disease.

Dubin-Johnson syndrome (DJS), an autosomal recessive disorder presenting with conjugated hyperbilirubinemia, is not associated with progression to chronic liver disease (CLD). Next-generation sequencing, application of bioinformatics pipeline, and segregation analysis were performed on 8 members of a consanguineous family with DJS and CLD. A novel variant, c.4406_4407delTA (p.Leu1469fs), in the ABCC2-gene in a homozygous state was found to be associated with DJS and CLD in proband and afflicted family members. DJS may not be a benign entity and novel genetic variants may be associated with progressive liver disease.

A Case of Dubin-Johnson Syndrome Presenting as Neonatal Cholestasis With Paucity of Interlobular Bile Ducts.

Dubin-Johnson syndrome (DJS) is a rare autosomal recessive disorder that typically manifests in young adulthood as jaundice with conjugated hyperbilirubinemia. We report a case presenting as neonatal cholestasis with the unexpected histologic finding of paucity of interlobular bile ducts, a feature that is not typically seen in DJS. The diagnosis was confirmed by absent canalicular multidrug-resistance-associated protein 2 (MRP2) immunohistochemical staining on liver biopsy tissue and molecular genetic testing that demonstrated heterozygous mutations in the ATP-Binding Cassette Subfamily C Member 2 (ABCC2) gene, including a novel missense mutation. This report describes a case of DJS with atypical clinicopathologic findings and suggests that DJS should be considered in patients with neonatal cholestasis and bile duct paucity.

Mutation spectrum and biochemical features in infants with neonatal Dubin-Johnson syndrome.

BACKGROUND: Dubin-Johnson syndrome (DJS) is an autosomal recessive disorder presenting as isolated direct hyperbilirubinemia.DJS is rarely diagnosed in the neonatal period. The purpose of this study was to clarify the clinical features of neonatal DJS and to analyze the genetic mutation of adenosine triphosphate-binding cassette subfamily C member 2 (ABCC2). METHODS: From 2013 to 2018, 135 infants with neonatal cholestasis at Seoul National University Hospital were enrolled. Genetic analysis was performed by neonatal cholestasis gene panel. To clarify the characteristics of neonatal DJS, the clinical and laboratory results of 6 DJS infants and 129 infants with neonatal cholestasis from other causes were compared. RESULTS: A total of 8 different ABCC2 variants were identified among the 12 alleles of DJS. The most common variant was p.Arg768Trp (33.4%), followed by p.Arg100Ter (16.8%). Three novel variants were identified (p.Gly693Glu, p.Thr394Arg, and p.Asn718Ser). Aspartate transaminase (AST) and alanine transaminase (ALT) levels were significantly lower in infants with DJS than in infants with neonatal cholestasis from other causes. Direct bilirubin and total bilirubin were significantly higher in the infants with DJS. CONCLUSIONS: We found three novel variants in 6 Korean infants with DJS. When AST and ALT levels are normal in infants with neonatal cholestasis, genetic analysis of ABCC2 permits an accurate diagnosis.

A recurrent ABCC2 p.G693R mutation resulting in loss of function of MRP2 and hyperbilirubinemia in Dubin-Johnson syndrome in China.

BACKGROUND: Dubin-Johnson syndrome (DJS) is a rare autosomal recessive disorder characterized by predominantly conjugated hyperbilirubinemia that is caused by pathogenic mutations in the adenosine triphosphate-binding cassette subfamily C member 2 (ABCC2) gene, which encodes multidrug resistance-associated protein 2 (MRP2). However, little is known about the causative mutation of DJS in China. Recently, we have reported ABCC2 p.G693R mutation in two unrelated cases. In the present study, we investigated the pathogenicity of the ABCC2 p.G693R mutation in DJS in China. METHODS: Clinical and genetic analysis was conducted for the two patients with the ABCC2 p.G693R mutation. Whole exome sequencing for mutations in other known hyperbilirubinemia-related genes was conducted for the cases with ABCC2 p.G693R. Expression and cellular localization of the mutant MRP2 p.G693R were analyzed by Western blotting and immunofluorescence assay, respectively. Organic anion transport activity was evaluated by the analysis of glutathione-conjugated-monochlorobimane. RESULTS: The two DJS patients with ABCC2 p.G693R mutation, which was conserved among different species, showed typical hyperbilirubinemia phenotype. No pathogenic mutation was identified in the other known hyperbilirubinemia related genes. Functional studies in three cell lines showed that the expression, localization and the organic anion transport activity were significantly compromised by MRP2 p.G693R mutation compared with wild-type MRP2. CONCLUSIONS: The recurrent ABCC2 p.G693R mutation is associated with loss of function of the MRP2 protein and may result in hyperbilirubinemia in DJS in China.

Genetic contribution of ABCC2 to Dubin-Johnson syndrome and inherited cholestatic disorders.

BACKGROUND AND AIMS: The ABCC2 gene is implicated in Dubin-Johnson syndrome (DJS), a rare autosomal recessive liver disorder. The primary aim of this study was to determine the diagnostic value of ABCC2 genetic testing in the largest cohort of DJS reported to date. The high number of patients with cholestatic manifestations in this series prompted us to evaluate the genetic contribution of rare, potentially pathogenic ABCC2 variants to other inherited cholestatic disorders. METHODS: The cohort study included 32 patients with clinical DJS diagnosis, and 372 patients referred for the following disorders: low phospholipid-associated cholelithiasis (LPAC) syndrome, intrahepatic cholestasis of pregnancy (ICP) and benign recurrent intrahepatic cholestasis (BRIC). ABCC2 was screened by next-generation sequencing. RESULTS: Most patients with clinical DJS had positive genetic diagnosis (n = 30; 94%), with a great diversity of point mutations and copy number variations in ABCC2. Strikingly, eight (27%) of these patients showed transient cholestatic features at presentation: four neonatal cholestasis, two ICP, one contraceptive-induced cholestasis and one sporadic cholestasis. Conversely, the frequency of rare, heterozygous, potentially pathogenic ABCC2 variants in patients with LPAC, ICP or BRIC did not differ significantly from that of the general population. CONCLUSIONS: This large series reveals that DJS is a highly homogeneous Mendelian disorder involving a large spectrum of ABCC2 variants. Genetic testing is crucial to establish early DJS diagnosis in patients with atypical presentations, such as neonatal cholestasis. This study also provides no evidence for the contribution of rare, potentially pathogenic ABCC2 variants to other inherited cholestatic disorders.

[Clinical features and ABCC2 genotypic analysis of an infant with Dubin-Johnson syndrome].

Dubin-Johnson syndrome (DJS) is an autosomal recessive disorder resulting from biallelic mutations of ABCC2 gene, with long-term or intermittent conjugated hyperbilirubinemia being the main clinical manifestation. This paper aims to report the clinical features and ABCC2 genotypes of an infant with DJS. A 9.5-month-old male infant was referred to the hospital due to abnormal liver function discovered over 9 months. The major clinical presentation was prolonged jaundice since neonatal period. A series of biochemistry analysis revealed markedly elevated total bilirubin, conjugated bilirubin and total bile acids. The patient had been managed in different hospitals, but the therapeutic effects were unsatisfactory due to undetermined etiology. Physical examination revealed jaundiced skin and sclera, and a palpable liver 3 cm below the right subcostal margin with medium texture. The spleen was not enlarged. Genetic analysis revealed a splice-site variant c.3988-2A>T and a nonsense variant c.3825C>G (p.Y1275X) in the ABCC2 gene of the infant, which were inherited from his mother and father respectively. The former had not been previously reported. Then ursodeoxycholic acid and phenobarbital were given orally. Half a month later, as a result, his jaundice disappeared and the biochemistry indices improved. However, the long-term outcome needs to be observed. Literature review revealed that neonates/infants with DJS presented with cholestatic jaundice soon after birth as the major clinical feature, and the ABCC2 variants exhibited marked heterogeneity.