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.

Hiperbilirrubinemias hereditarias: un diagnóstico diferencial a considerar en ictericia / Hereditary hiperbilirrubinemias: a differential diagnosis to considerer in icterus

Las hiperbilirrubinemias hereditarias (HBH) son patologías originadas por defectos en las enzimas y proteínas que participan del metabolismo de la bilirrubina. El clearence de bilirrubina incluye captación y almacenamiento en hepatocitos, conjugación, excreción hacia la bilis y recaptura de su forma conjugada por hepatocitos. Las HBH varían de acuerdo a su patogenia, presentación clínica, niveles de bilirrubinemia y tratamientos disponibles. En general son poco frecuentes, a excepción del Síndrome de Gilbert. Están las que son de predominio indirecto, como el Síndrome de Gilbert y el de Crigler-Najjar, y las de predominio directo, como el Síndrome de Dubin-Johnson y el de Rotor. En general no requieren tratamiento específico y tienen curso benigno, a excepción del Síndrome de Crigler-Najjar para el cual existen medidas terapéuticas específicas a considerar, teniendo un pronóstico reservado para algunas de sus formas de presentación. Es importante el conocimiento de estos síndromes dado el alto índice de sospecha requerido para su diagnóstico y para su diferenciación de otras patologías hepatobiliares de mayor riesgo y severidad.

Hereditary hiperbilirrubinemias (HBH) are pathologies originated from the defect of the enzymes and proteins involved in the metabolism of bilirubin. The bilirubin clearance includes uptake and storage in hepatocytes, conjugation, excretion into bile and recapture of its conjugated form by hepatocytes. HBH vary according to their pathogenesis, clinical presentation, levels of bilirubin and available treatments. Generally they are infrequent, except for Gilbert Syndrome. There are those with indirect bilirubin predominance, such as Gilbert and Crigler-Najjar syndromes, and those with direct bilirubin predominance, including Dubin-Johnson and Rotor syndromes. In general, they do not require specific treatment and have a benign course, with the exception of the Crigler-Najjar Syndrome, for which there are specific therapeutic measures to consider, as well as a reserved prognosis for some of their forms of presentation. The knowledge of these syndromes is important 2 given the high index of suspicion required for its diagnosis and for its differentiation from other hepatobiliary pathologies of greater risk and severity.

Clinical utility of next-generation sequencing in the diagnosis of hereditary haemolytic anaemias.

Hereditary haemolytic anaemias are genetically and phenotypically heterogeneous disorders characterized by increased red cell destruction, with consequences ranging from innocuous to severe life-threatening anaemia. Diagnostic laboratories endeavour to assist clinicians reach the exact patient diagnosis by using tests principally based on morphological and biochemical techniques. However, these routine studies may be inconclusive, particularly in newborn infants and when transfusions have recently been administered. Large numbers and size of the potentially involved genes also impose a practical challenge for molecular diagnosis using routine sequencing approaches. To overcome these diagnostic shortcomings, we have utilized next-generation sequencing to provide a high-throughput, highly sensitive assay. We developed a panel interrogating 28 genes encoding cytoskeletal proteins and enzymes with sequencing coverage of the coding regions, splice site junctions, deep intronic and regulatory regions. We then evaluated 19 samples, including infants with unexplained extreme hyperbilirubinaemia and patients with transfusion-dependent haemolytic anaemia. Where possible, inheritance patterns of pathogenic mutations were determined by sequencing of immediate relatives. We conclude that this next-generation sequencing panel could be a cost-effective approach to molecular diagnosis of hereditary haemolytic anaemia, especially when the family history is uninformative or when routine laboratory testing fails to identify the causative haemolytic process.

Unusual presentation of Gilbert disease with high levels of unconjugated bilirubin. Report of two cases

Gilbert’s syndrome is a benign condition characterized by asymptomatic sporadic episodes of jaundice, due to a mild unconjugated hyperbilirubinemia caused by a deficiency in bilirubin glucoronidation. Under certain physiologic or pathologic events, bilirubin level rises but according to literature it does not reach out more than 3 mg/dl. We report 2 cases of Gilbert’s syndrome, genetically tested, which presented with bilirubin levels above 6 mg/dl without any trigger or coexisting condition. In conclusion, bilirubin levels higher than 6 mg/dl in Gilbert syndrome are rare, hemolytic and other metabolism diseases must be ruled out, and enetic testing may be necessary in some cases (AU)

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Causes of prolonged jaundice in infancy: 3-year experience in a tertiary paediatric centre.

UNLABELLED: Although prolonged jaundice (PJ) commonly occurs in infancy, there is not yet agreement as to the appropriate extent of investigations, particularly in otherwise well children. Significant pathologies may present with PJ in this age group and need to be considered. AIM: The aim of this retrospective study was to ascertain the causes of PJ in infants referred to a single tertiary paediatric centre. METHODS: Infants referred with PJ over a 3-year period were identified. Clinical documentation, electronic notes and results of investigations performed prior to and after referral were reviewed. RESULTS: One hundred and sixty-seven infants with PJ were seen. Fifty-eight percent were over 28 days of age. Four patients had conjugated hyperbilirubinaemia. Eighteen percent of patients were found to have a specific medical diagnosis causing or contributing to PJ, almost half of whom had normal clinical examination. The single most common pathological cause for PJ was hypothyroidism found in six patients. CONCLUSIONS: This study demonstrates that normal clinical examination and exclusion of conjugated hyperbilirubinaemia are insufficient to exclude pathological causes of PJ. Overall, these children were referred late. Guidelines, in conjunction with education initiatives, are required to optimise the management of prolonged jaundice in infancy.

Inherited disorders of bilirubin clearance.

Inherited disorders of hyperbilirubinemia may be caused by increased bilirubin production or decreased bilirubin clearance. Reduced hepatic bilirubin clearance can be due to defective (i) unconjugated bilirubin uptake and intrahepatic storage, (ii) conjugation of glucuronic acid to bilirubin (e.g., Gilbert syndrome, Crigler-Najjar syndrome, Lucey-Driscoll syndrome, breast milk jaundice), (iii) bilirubin excretion into bile (Dubin-Johnson syndrome), or (iv) conjugated bilirubin re-uptake (Rotor syndrome). In this review, the molecular mechanisms and clinical manifestations of these conditions are described, as well as current approaches to diagnosis and therapy.

Radionuclide cholescintigraphy in genetically confirmed Rotor syndrome.

A 7-year-old girl had been followed up for persistent conjugated hyperbilirubinemia since birth. Alanine aminotransferase, aspartate aminotransferase and γ-glutamyl transpeptidase activity was within the normal range, and liver protein synthesis had always been normal. Infectious etiology of jaundice, autoimmune diseases, drug-induced liver injury, hemolytic anemia, α-1 anti-trypsin deficiency, Wilson disease and Gilbert syndrome were ruled out. At the age of 8 years the patient underwent radionuclide dynamic cholescintigraphy, indicating poor accumulation of the radiotracer in the liver on one hand, and severe retention of the radiopharmaceutical in the blood pool (including the heart) on the other hand. Rotor syndrome was suspected and finally confirmed on molecular analysis. This case represents the first cholescintigraphy report in a pediatric patient with genetically proven Rotor syndrome.

Gene replacement therapy for genetic hepatocellular jaundice.

Jaundice results from the systemic accumulation of bilirubin, the final product of the catabolism of haem. Inherited liver disorders of bilirubin metabolism and transport can result in reduced hepatic uptake, conjugation or biliary secretion of bilirubin. In patients with Rotor syndrome, bilirubin (re)uptake is impaired due to the deficiency of two basolateral/sinusoidal hepatocellular membrane proteins, organic anion-transporting polypeptide 1B1 (OATP1B1) and OATP1B3. Dubin-Johnson syndrome is caused by a defect in the ATP-dependent canalicular transporter, multidrug resistance-associated protein 2 (MRP2), which mediates the export of conjugated bilirubin into bile. Both disorders are benign and not progressive and are characterised by elevated serum levels of mainly conjugated bilirubin. Uridine diphospho-glucuronosyl transferase 1A1 (UGT1A1) is responsible for the glucuronidation of bilirubin; deficiency of this enzyme results in unconjugated hyperbilirubinaemia. Gilbert syndrome is the mild and benign form of inherited unconjugated hyperbilirubinaemia and is mostly caused by reduced promoter activity of the UGT1A1 gene. Crigler-Najjar syndrome is the severe inherited form of unconjugated hyperbilirubinaemia due to mutations in the UGT1A1 gene, which can cause kernicterus early in life and can be even lethal when left untreated. Due to major disadvantages of the current standard treatments for Crigler-Najjar syndrome, phototherapy and liver transplantation, new effective therapeutic strategies are under development. Here, we review the clinical features, pathophysiology and genetic background of these inherited disorders of bilirubin metabolism and transport. We also discuss the upcoming treatment option of viral gene therapy for genetic disorders such as Crigler-Najjar syndrome and the possible immunological consequences of this therapy.

Hyperbilirubinemia syndromes (Gilbert-Meulengracht, Crigler-Najjar, Dubin-Johnson, and Rotor syndrome).

Hyperbilirubinemia is an important clinical sign that often indicates severe hepatobiliary disease of different etiologies. Inherited non-haemolytichyperbilirubinemic conditions include Dubin-Johnson, Rotor, and Gilbert-Meulengracht syndromes, which are important differential diagnoses indicating benign disease that require no immediate treatment. Dubin-Johnson and Rotor syndromes are rare, exhibit mixed direct and indirect hyperbilirubinemia as well as typical profiles or urinary coproporphyrin excretion. Gilbert-Meulengracht disease leads to unconjugated hyperbilirubinemia because of impaired glucuronidation activity, and is part of a spectrum of genetic variants also encompassing fatal Crigler-Najjar syndrome. Gilbert-Meulengracht syndrome can be diagnosed by clinical presentation, biochemistry and genotyping, and carries significance regarding the disposition towards drug-associated toxicity. In addition, the precise diagnosis of these inherited hyperbilirubinemic syndromes avoids unnecessary invasive procedures for suspected more severe hepatobiliary disease.

[Hereditary pigmentary hepatoses (functional hyperbilirubinemias)].

Reviewed in this paper are bilirubin metabolism, definition and classification of hereditary pigmentary hepatoses, their pathogenesis and forms of inheritance, clinical picture, laboratory, instrumental and differential diagnosis, morphological changes in the hepatic tissue, and therapeutic strategies.

The patient presenting with isolated hyperbilirubinemia.

Hyperbilirubinemia is a common laboratory finding in clinical practice, being found in several haematological and liver diseases as well as in familial conditions (5-10% in Western countries). Although most of the familial forms of hyperbilirubinemia are classically viewed as benign conditions, they have gained an increased interest in the last few years since recent data have indicated that subjects with an impaired bilirubin metabolism may have an increased susceptibility to drug toxicity. The authors briefly review the main steps of bilirubin metabolism, with a special emphasis on the emerging concepts on the molecular mechanisms of regulation by nuclear receptors (NRs) and genetic factors. Then the different forms of isolated hyperbilirubinemia occurring in both adults and paediatrics are systematically analysed, and a new categorisation is also proposed in light of the recent advances in bilirubin research. Finally, a diagnostic algorithm is discussed, along with a correct approach to its management, in order to avoid unnecessary medical investigations.

Hereditary spherocytosis coexisting with Gilbert's syndrome: a diagnostic dilemma.

Haemolytic anaemia generally gives rise to only a modest elevation of serum bilirubin. Unconjugated hyperbilirubinaemia of an extreme degree should raise suspicion of additional factors, such as Gilbert's syndrome, hepatocellular dysfunction or renal failure. We present a 17-year-old boy with hereditary spherocytosis coexisting with Gilbert's syndrome.

[The Dubin-Johnson syndrome: case report and review of literature]. / Síndrome de Dubin Johnson: presentación de un caso y revisión de la literatura.

The Dubin-Johnson syndrome is a hereditary deficiency in the excretion ofconjugated bilirrubin by hepatocytes characterized by chronic hyperbilirubinemia, alteration in coproporphyrin metabolism, and intracellular deposition of a dark melanin-like pigment giving the liver a typical black cast. We report a 28-year-old male patient who presented conjunctival jaundice and conjugated-hyperbilirubinemia without no other alteration in hepatic biochemistry. The diagnosis of this syndrome was perfomed by using the low-risk methods of laparoscopy-facilitated hepatic biopsy and oral cholecystography In contrast, we avoided the classical Bromsulphalein test because of potential severe side effects. We stress here the current importance of these tests for confirming the diagnosis. By using this methodology, we were not able to quantify the isomeric profile of the urinary coproporphyrins nor 99mTc-HIDA cholescintigraphy. In conclusion, we confirm the utility of hepatic biopsy with the aid of laparoscopy and oral cholecystography for the diagnosis of the Dubin-Johnson syndrome on the basis of their effectiveness and relative lack of complications.

Rotor-type hyperbilirubinaemia has no defect in the canalicular bilirubin export pump.

BACKGROUND: The cause of Rotor syndrome (RS), a rare-familial conjugated hyperbilirubinaemia with normal liver histology, is unclear. We hypothesized that RS can be an allelic variant of Dubin-Johnson syndrome, caused by mutation in ABCC2, and investigated ABCC2 (gene) and ABCC2 (protein) in two patients with RS. METHODS: A 57-year-old male presented with a 5-year history of predominantly conjugated hyperbilirubinaemia (170 micromol/l). Urinary porphyrin excretion was increased; cholescintigraphy revealed no chromoexcretion. A 68-year-old male presented with lifelong conjugated hyperbilirubinaemia (85 micromol/l). Bromosulfophthalein elimination was typical for RS. Both patients had histologically normal liver, without pigment. ABCC2 expression was investigated by confocal fluorescence microscopy. ABCC2 was sequenced from genomic DNA and cDNA, and exon deletions/duplications were sought by comparative genomic hybridization on a custom micro-array. RESULTS: In both patients, ABCC2 was expressed unremarkably at the apical membrane of hepatocytes and no sequence alterations were found in 32 exons, adjacent intronic regions and the promoter region of ABCC2. CONCLUSIONS: Rotor-type hyperbilirubinaemia is not an allelic variant of ABCC2 deficiency.

[A case with Rotor syndrome in hyperbilirubinemic family].

Rotor syndrome is a rare, benign familial disorder characterized by chronic fluctuating, nonhemolytic and predominantly conjugated hyperbilirubinemia with normal hepatic histology. In contrast to Dubin-Johnson syndrome, there is no liver pigmentation in Rotor syndrome. A 36-year-old man was admitted due to asymptomatic persistent jaundice. His siblings had jaundice with direct hyperbilirubinemia. Physical examination revealed icteric sclerae without hepatosplenomegaly. Laboratory findings showed increased serum bilirubin with direct bilirubinemia. Hepatic uptake and storage capacity of indocyanine green was markedly reduced, while excretion into bile was slightly suppressed. Markedly decreased hepatic uptake and poor visualization of the gallbladder and biliary tract were shown in 99mTc-DISIDA scan. Histology of the liver showed mild steatosis without pigmentation. We report a case with the review of literature.

A Case with Rotor Syndrome in Hyperbilirubinemic Family / 대한소화기학회지

Rotor syndrome is a rare, benign familial disorder characterized by chronic fluctuating, nonhemolytic and predominantly conjugated hyperbilirubinemia with normal hepatic histology. In contrast to Dubin-Johnson syndrome, there is no liver pigmentation in Rotor syndrome. A 36-year-old man was admitted due to asymptomatic persistent jaundice. His siblings had jaundice with direct hyperbilirubinemia. Physical examination revealed icteric sclerae without hepatosplenomegaly. Laboratory findings showed increased serum bilirubin with direct bilirubinmia. Hepatic uptake and storage capacity of indocyanine green was markedly reduced, while excretion into bile was slightly suppressed. Markedly decreased hepatic uptake and poor visualization of the gallbladder and biliary tract were shown in 99mTc-DISIDA scan. Histology of the liver showed mild steatosis without pigmentation. We report a case with the review of literature.

Primary shunt hyperbilirubinaemia in a large four-generation family confirming autosomal dominant genetic disorder.

AIM: To describe the pattern of inheritance and confirm the diagnostic criteria of primary shunt hyperbilirubinaemia (PSH). METHODS: Forty members of a family pedigree across four generations were included in this study. All family members were interviewed and investigated by physical examination, hematology and liver function test and the pattern of inheritance was analyzed. RESULTS: Nine of the forty family members suffered primary shunt hyperbilirubinaemia. The mature erythrocytes of the propositus were irregular in shape and size. The pedigree showed transmission of the trait through four generations with equal distribution in male and female. No individual with a primary shunt hyperbilirubinaemia was born to unaffected parents. The penetrance was complete in adult. CONCLUSION: The pattern of inheritance is autosomal dominant. The abnormality of erythrocytes and decrease in white blood cell could be supplemented in the diagnosis of PSH. The PSH is a genetic disorder and could by renamed as hereditary shunt hyperbilirubinaemia.

[Molecular diagnosis of heritable unconjugated hyperbilirubinemias].

There is considerable evidence suggesting that genetic damages to human uridine diphosphate glucuronyltransferase (UDPGT) gene located on clhromosome 2q37 are responsible for hereditary unconjugated hyperbilirubinemias (HUHB). The Crigler-Najjar syndrome of types I and II is characterized by structural mutations on one of 5 exons of HUHB gene, resulting in the synthesis of defective catalytically inactive isoforms of the enzyme. In Gilbert's syndrome, genetic alterations are located at the promoter of the gene and accompanied by the nucleotide insert of thymine adenine (TA). Promoter prolongation impairs the binding of IID transcription factor and leads to the decreased production of the enzyme UDPGT 1,1. Examination of the molecular epidemiology of gene mutations of UDPGT 1,1 that is typical of Gilbert's syndrome ascertained a great difference in the indices, from 2 to 16% in the Asian and European populations, respectively. In addition to polymerase chain reaction, high performance liquid chromatography may be used for the diagnosis of genetic alterations in Gilbert's syndrome.

Congenital nonhemolytic hyperbilirubinemias.

Congenital nonhemolytic hyperbilirubinemias (CNH) are quite rare pathology of liver. They occur most often in children, but are common in adults too. A common feature of congenital nonhemolytic hyperbilirubinemias is an abnormal serum bilirubin level without other abnormalities in routine liver functional tests. Liver histology on light microscopy is normal. Hereditary genetics defect of enzymes taking part in metabolism of bilirubin is the cause of CNH. They are divided into two groups: with unconjugated hyperbilirubinemia (Crigler-Najjar syndrome, Gilbert syndrome) and conjugated hyperbilirubinemia (Dubin-Johnson syndrome and Rotor syndrome). Because CNH in adults are benign disorders and the prognosis is excellent, patients do not require any specific therapy. Is important to take the differential diagnosis. Once the diagnosis of congenital nonhemolytic hyperbilirubinemia is confirmed, patients should be informed of the disease process and its benign nature to prevent needless work-up in the future. In present, CNH are treated as cosmetic defects and no therapy is applied.