Novel ATP8B1 mutation in an adult male with progressive familial intrahepatic cholestasis

Progressive familial intrahepatic cholestasis type 1 is a rare disease that is characterized by low serum γ-glutamyltransferase levels due to mutation in ATP8B1. We present a 23-year-old male who experienced persistent marked pruritus for eighteen years and recurrent jaundice for thirteen years, in addition to cholestasis that eventually became fatal. Genetic sequencing studies of the entire coding (exon) sequences of ATP8B1 and ABCB11 uncovered a novel heterozygous missense 3035G>T mutation (S1012I) and a synonymous 696T>C mutation in ATP8B1. The patient’s progression was associated with not only impaired familial intrahepatic cholestasis 1 (FIC1) function but also impaired bile salt export pump expression due to the impaired FIC1 function. Our findings show that patients with intermittent cholestasis can develop progressive liver disease even after several decades and require regular follow up.     

Familial cholestasis: progressive familial intrahepatic cholestasis, benign recurrent intrahepatic cholestasis and intrahepatic cholestasis of pregnancy

Progressive familial intrahepatic cholestasis (PFIC) type 1, 2 and 3 are due to mutations in ATP8B1, ABCB11 and ABCB4, respectively. Each of these genes encodes a hepatocanalicular transporter, which is essential for the proper formation of bile. Mutations in ABCB4 can result in progressive cholestatic disease, while mutations in ATP8B1 and ABCB11 can result both in episodic cholestasis, referred to as benign recurrent intrahepatic cholestasis (BRIC) type 1 and 2, as well as in progressive cholestatic disease. This suggests a clinical continuum and these diseases are therefore preferably referred to as ATP8B1 deficiency and ABCB11 deficiency. Similarly PFIC type 3 is designated as ABCB4 deficiency. Heterozygous mutations in each of these transporters can also be associated with intrahepatic cholestasis of pregnancy. This review summarizes the pathophysiology, clinical features and current as well as future therapeutic options for progressive familial- and benign recurrent intrahepatic cholestasis as well as intrahepatic cholestasis of pregnancy.     

Hereditäre Defekte hepatobiliärer Transportproteine

Defects in transport proteins that are expressed at the hepatocyte canalicular membrane can cause severe impairment of hepatobiliary transport processes. Progressive familial intrahepatic cholestasis (PFIC) typically manifests in early childhood. Genetic variants in the aminophospholipid transporter FIC1 (ATP8B1 gene) cause PFIC1, characterized by elevated serum bile acids but normal or only mildly elevated gamma-GT levels. Benign recurrent intrahepatic cholestasis type 1 (BRIC1) is also caused by ATP8B1 mutations. Defects in the function of the bile salt efflux pump (BSEP; ABCB11) cause PFIC2 or BRIC2, depending on the degree of BSEP impairment. A common BSEP variant, the V444A polymorphism, is commonly found in various types of cholestatic liver injury, including drug-induced liver injury. Finally, dysfunction of the multidrug resistance gene product MDR3 (ABCB4) leads to PFIC3, characterized by low biliary phospholipids and high gamma-GT levels in serum due to bile duct injury. All three transporter genes are also associated with intrahepatic cholestasis of pregnancy. Treatment options include ursodeoxycholic acid for milder forms and liver transplantation for severe pediatric cases.     

Benign recurrent intrahepatic cholestasis type 2 is caused by mutations in ABCB11

BACKGROUND & AIMS: Progressive familial intrahepatic cholestasis (PFIC) and benign recurrent intrahepatic cholestasis (BRIC) are hereditary liver disorders; PFIC is characterized by severe progressive liver disease whereas BRIC patients have intermittent attacks of cholestasis without permanent liver damage. Mutations in ATP8B1 are present in PFIC type 1 and in a subset of BRIC patients. We hypothesized that a genetically distinct form of BRIC is associated with mutations in ABCB11. This gene encodes the bile salt export pump (BSEP) and is mutated in PFIC type 2. METHODS: Patients from 20 families were included; all had a normal ATP8B1 sequence. Sequencing of all 27 coding exons including the splice junctions of ABCB11 revealed 8 distinct mutations in 11 patients from 8 different families: one homozygous missense mutation (E297G) previously described in PFIC2 patients, 6 novel missense mutations, and one putative splice site mutation. RESULTS: In 12 families, no mutations in ATB8B1 or ABCB11 were detected. Pancreatitis is a known extrahepatic symptom in BRIC caused by ATP8B1 mutations, but was not present in BRIC patients with mutations in ABCB11. In contrast, cholelithiasis was observed in 7 of 11 BRIC patients with mutations in ABCB11, but has not been described in ATP8B1-affected BRIC patients. CONCLUSIONS: Mutations in ABCB11 are associated with BRIC, and consistent with the genetic classification of PFIC into 2 subtypes, we propose that this disorder be named BRIC type 2.     

Adult progressive intrahepatic cholestasis associated with genetic variations in ATP8B1 and ABCB11

Severe intrahepatic cholestasis with low serum γ-glutamyltranspeptidase (γ-GT) activity is exceptionally rare in adult patients, and its association with multi-genetic alterations of bile salt transporters has not been reported. We investigated a 25-year-old man presenting with a four-year history of jaundice. Laboratory and radiographic examinations revealed clinical pictures of progressive intrahepatic cholestasis with low γ-GT. Serial liver histopathology demonstrated cirrhosis resulting from progressive persistent cholestatic injury. Genetic sequencing studies for the entire coding exons of ATP8B1 and ABCB11 uncovered a heterozygous missense mutation 1798 C->T (R600W) in ATP8B1 , and a homozygous nucleotide substitution 1331 T->C (V444A) in ABCB11 . In conclusion, this is a rare case of adult onset progressive intrahepatic cholestasis with low γ-GT associated with heterozygous ATP8B1 mutation and homozygous ABCB11 polymorphism. Further studies are necessary to investigate the impact of heterozygous R600W mutation and whether other cholestatic disorders are multi-genetic.     

Recurrent intrahepatic cholestasis of pregnancy and chain-like choledocholithiasis in a female patient with stop codon in the ABDC4-gene of the hepatobiliary phospholipid transporter

We report the case of a 40-years-old female patient with recurrent cholestatic liver disease who presented twice with severe intrahepatic cholestasis of pregnancy and pronounced choledocholithiasis between pregnancies. Bile duct stones were removed endoscopically and a laparoscopic cholecystectomy was performed after the second pregnancy. Liver histology revealed intrahepatic cholestasis with portal inflammation and fibrosis, resembling progressive familial intrahepatic cholestasis (PFIC). Molecular genetic studies identified the heterozygous mutation c.957C > T in the ABCB4 gene encoding the hepatobiliary phospholipid transporter. This is the first report of this mutation that introduces a stop codon in an index patient with intrahepatic cholestasis of pregnancy and multiple bile duct stones. In addition, we detected the ABCB11 polymorphism V 444A, which is associated with a decreased expression of the bile salt export pump. Whereas homozygous carriers of the ABCB4 mutation develop PFIC type 3, the heterozygous ABC transporter mutations represent genetic risk factors for cholelithiasis and recurrent cholestatic hepatitis upon challenge with oral contraceptives or during pregnancy. Of note, the patient presented with normal serum gamma-glutamyltranspeptidase activities during pregnancy-associated cholestatic episodes but normal liver enzymes after delivery, whereas choledocholithiasis was associated with high gamma-glutamyl transpeptidase levels. It is unknown whether ursodeoxycholic acid prevents cholestasis or gallstones in patients with ABCB4 deficiency.     

3例良性复发性肝内胆汁淤积症患者临床特点分析

目的 总结和分析良性复发性肝内胆汁淤积症(BRIC)患者的临床特征。方法 回顾性分析3例在复旦大学附属中山医院诊治的BRIC患者的一般情况、临床表现、实验室检查、影像学检查、病理学检查和分子遗传学检查等临床资料。结果 3例患者均为男性,首次发病年龄小于20岁,除外其他已知的可致胆汁淤积的病因;3例患者疾病均反复发作,但具有一定的自限性,发作时有黄疸和皮肤瘙痒表现,其中2例伴大便不规律、腹胀和食欲下降;实验室检查显示血清总胆红素和直接胆红素、碱性磷酸酶和总胆汁酸水平显著升高,而γ-谷氨酰转肽酶和转氨酶水平正常或轻度升高;MRCP检查均未见有肝内外胆管异常;2例肝组织病理学检查提示肝细胞明显胆汁淤积伴毛细胆管栓塞形成;3例患者均有功能预测为“潜在有害”或致病分级为“可能致病”的ATP8B1基因突变位点检出。结论 目前,BRIC病例报道较少,发病机制未完全明确,诊断较困难。临床医生应在排除其他常见肝损伤病因后,综合分析其临床表现、辅助检查和病理学检查结果进行综合临床诊断。对于临床高度怀疑BRIC的患者,应尽早行分子遗传学检查,以明确诊断,指导治疗。     

Expanding etiology of progressive familial intrahepatic cholestasis

BACKGROUND Progressive familial intrahepatic cholestasis(PFIC) refers to a disparate group of autosomal recessive disorders that are linked by the inability to appropriately form and excrete bile from hepatocytes, resulting in a hepatocellular form of cholestasis. While the diagnosis of such disorders had historically been based on pattern recognition of unremitting cholestasis without other identified molecular or anatomic cause, recent scientific advancements have uncovered multiple specific responsible proteins. The variety of identified defects has resulted in an ever-broadening phenotypic spectrum, ranging from traditional benign recurrent jaundice to progressive cholestasis and end-stage liver disease.AIM To review current data on defects in bile acid homeostasis, explore the expanding knowledge base of genetic based diseases in this field, and report disease characteristics and management.METHODS We conducted a systemic review according to PRISMA guidelines. We performed a Medline/PubMed search in February-March 2019 for relevant articles relating to the understanding, diagnosis, and management of bile acid homeostasis with a focus on the family of diseases collectively known as PFIC. English only articles were accessed in full. The manual search included references of retrieved articles.We extracted data on disease characteristics, associations with other diseases, and treatment. Data was summarized and presented in text, figure, and table format.RESULTS Genetic-based liver disease resulting in the inability to properly form and secrete bile constitute an important cause of morbidity and mortality in children and increasingly in adults. A growing number of PFIC have been described based on an expanded understanding of biliary transport mechanism defects and the development of a common phenotype.CONCLUSION We present a summary of current advances made in a number of areas relevant to both the classically described FIC1(ATP8 B1), BSEP(ABCB11), and MDR3(ABCB4) transporter deficiencies, as well as more recently described gene mutations--TJP2(TJP2), FXR(NR1 H4), MYO5 B(MYO5 B), and others which expand the etiology and understanding of PFIC-related cholestatic diseases and bile transport.     

Novel resequencing chip customized to diagnose mutations in patients with inherited syndromes of intrahepatic cholestasis

BACKGROUND & AIMS: Inherited syndromes of intrahepatic cholestasis commonly result from mutations in the genes SERPINA1 (alpha(1)-antitrypsin deficiency), JAG1 (Alagille syndrome), ATP8B1 (progressive familial intrahepatic cholestasis type 1 [PFIC1]), ABCB11 (PFIC2), and ABCB4 (PFIC3). However, the large gene sizes and lack of mutational hotspots make it difficult to survey for disease-causing mutations in clinical practice. Here, we aimed to develop a technological tool that reads out the nucleotide sequence of these genes rapidly and accurately. METHODS: 25-mer nucleotide probes were designed to identify each base for all exons, 10 bases of intronic sequence bordering exons, 280-500 bases upstream from the first exon for each gene, and 350 bases of the second intron of the JAG1 gene and tiled using the Affymetrix resequencing platform. We then developed high-fidelity polymerase chain reactions to produce amplicons using 1 mL of blood from each subject; amplicons were hybridized to the chip, and nucleotide calls were validated by standard capillary sequencing methods. RESULTS: Hybridization of amplicons with the chip produced a high nucleotide sequence readout for all 5 genes in a single assay, with an automated call rate of 93.5% (range, 90.3%-95.7%). The accuracy of nucleotide calls was 99.99% when compared with capillary sequencing. Testing the chip on subjects with cholestatic syndromes identified disease-causing mutations in SERPINA1, JAG1, ATP8B1, ABCB11, or ABCB4. CONCLUSIONS: The resequencing chip efficiently reads SERPINA1, JAG1, ATP8B1, ABCB11, and ABCB4 with a high call rate and accuracy in one assay and identifies disease-causing mutations.     

Familial intrahepatic cholestasis: New and wide perspectives

BackgroundProgressive familial intrahepatic cholestasis (PFIC) includes autosomal recessive cholestatic rare diseases of childhood.AimsTo update the panel of single genes mutations involved in familial cholestasis.MethodsPubMed search for “familial intrahepatic cholestasis” alone as well as in combination with other key words was performed considering primarily original studies and meta-analyses.ResultsPFIC1 involves ATP8B1 gene encoding for aminophospholipid flippase FIC1. PFIC2 includes ABCB11 gene, encoding for protein functioning as bile salt export pump. PFIC3 is due to mutations of ABCB4 gene responsible for the synthesis of class III multidrug resistance P-glycoprotein flippase. PFIC4 and PFIC5 involve tight junction protein-2 gene and NR1H4 gene encoding for farnesoid X receptor. Benign Intrahepatic Cholestasis, Intrahepatic Cholestasis of Pregnancy and Low-phospholipid-associated cholelithiasis involve the same genes and are characterized by intermittent attacks of cholestasis, no progression to cirrhosis, reversible pregnancy-specific cholestasis and cholelithiasis in young people. Blood and liver tissue levels of bile-excreted drugs can be influenced by the presence of mutations in PFIC genes, causing drug-induced cholestasis. Mutations in PFIC genes might increase the risk of liver cancer.ConclusionThere is a high proportion of unexplained cholestasis potentially caused by specific genetic pathophysiologic pathways. The use of next generation sequencing and whole-exome sequencing could improve the diagnostic process in this setting.     

Childhood cholestasis and bile transporters

Identification of the transport systems involved in bile secretion and of the genes codifying these systems has allowed the etiology of familial intrahepatic cholestasis to be determined in most affected children. Mutations in ATP8B1 cause a defect in FIC1, an aminophospholipid flipase, and give rise to a variable spectrum of disease, ranging from progressive intrahepatic cholestasis to benign recurrent cholestasis, due to alterations in the lipid composition of the membranes and decreased expression of the nuclear factor FXR. Mutations in ABCB11 cause a defect of the canalicular bile salt export pump (BSEP), with early clinical manifestations and progression to hepatocellular failure in childhood. Mutations in ABCB4 cause an alteration in the MDR3 phospholipid transporter, and a variable spectrum of disease from progressive ductal injury to cirrhosis in children, and gallstones, cholestasis of pregnancy, or late cirrhosis in adults.     

Differenzialdiagnose Ikterus

Jaundice is the result of increased serum bilirubin levels. An initial differentiation of the underlying causes can be made by distinguishing increased conjugated and non-conjugated serum bilirubin and the findings of abdominal ultrasound examination. This combined approach enables a first classification into extrahepatic causes, hepatocellular dysfunction and intrahepatic and extrahepatic forms of cholestasis. In each diagnostic category of jaundice the differential diagnosis can be improved by additional imaging techniques comprising helical CT scanning, MRCP or ERCP, targeted laboratory tests and finally a liver biopsy. Specific difficult-to-diagnose cholestatic diseases include primary biliary cirrhosis (PBC), primary sclerosing cholangitis (PSC), autoimmune hepatitis PBC and PSC overlap syndromes, IgG4 cholangiopathy and familial deficiency of biliary transporters due to mutations in the ATP8B1, ABCB11, ABCB4 and Jag1 genes. Molecular genetic testing enables these familial conditions to be differentiated.     

Bile salt export pump deficiency disease: two novel,late onset,ABCB11 mutations identified by next generation sequencing

Progressive familial intrahepatic cholestasis (PFIC) is a heterogeneous group of autosomal recessive cholestatic diseases of childhood and represents the main indication for liver transplantation at this age; PFIC2 involves ABCB11 gene, that encodes the ATP-dependent canalicular bile salt export pump (BSEP). Benign intrahepatic cholestasis (BRIC) identifies a group of diseases involving the same genes and characterized by intermittent attacks of cholestasis with no progression to liver cirrhosis. Diagnosis with standard sequencing techniques is expensive and available only at a few tertiary centers. We report the application of next generation sequencing (NGS) in the diagnosis of the familial intrahepatic cholestasis with a parallel sequencing of three causative genes. We identified the molecular defects in ABCB11 gene in two different probands who developed a severe cholestatic disease of unknown origin. In the first patient a compound heterozygosity for the novel frameshift mutation p.Ser1100GlnfsX38 and the missense variant p.Glu135Lys was detected. In the second patient, triggered by contraceptive therapy, we identified homozygosity for a novel mis-sense variant p.Ala523Gly. In conclusion, these mutations seem to have a late onset and a less aggressive clinical impact, acting as an intermediate form between BRIC and PFIC.     

Excessive bilirubin elevation in a patient with hereditary spherocytosis and intrahepatic cholestasis

Hereditary spherocytosis is a common hemolytic anemia with an estimated incidence of 1?/?2500 births. It is caused by a molecular defect in one or more of the proteins of the red blood cell cytoskeleton. Mutations in the ABCB11 gene, encoding the bile salt export pump, can entail progressive familial intrahepatic cholestasis and benign recurred intrahepatic cholestasis. A?18 year old Turkish patient with hereditary spherocytosis was admitted to hospital with pruritus and severe jaundice. Ultrasound examination presented stones in gallbladder and bile duct. After endoscopic retrograde cholangiography with extraction of small bile duct stones abdominal pain resolved and liver enzymes normalized within a few days, but bilirubin and bile acids remained highly elevated. Liver biopsy revealed a severe canalicular cholestasis. Genetic analysis showed the compound heterozygous variants ABCB11 A?444V and 3084A?>?G. Treatment with ursodesoxycholic acid and intermittent therapy with prednisone reduced pruritus and jaundice with concomitant improvement of blood test. Here we report the first case of a patient with combined hereditary spherocytosis and compound heterozygous ABCB11 gene variants predisposing to intrahepatic cholestasis. Therefore, patients with hemolytic disorders should be investigated for bile acid transporter diseases in case of hyperbilirubinemia and severe cholestasis.     

Advances in familial and congenital cholestatic diseases. Clinical and diagnostic implications

Recent progress in liver cell biology and molecular genetics revealed that a number of familial and congenital cholestatic disorders are caused by mutations in genes coding for hepatobiliary-transporter or for signalling proteins involved in morphogenesis. The status of the field is reviewed in the light of its impact on current diagnostic and clinical practice. The heterogeneous progressive familial intrahepatic cholestasis can now be separated into different genetic diseases. FIC1-defective progressive familial intrahepatic cholestasis (previously Byler disease) is determined by mutations in the FIC1 gene, coding for P-type ATPases of unknown physiological function, while a second form (bile salt export pump defective progressive familial intrahepatic cholestatis) is caused by a defective function of the canalicular bile salt export pump. Furthermore, a group of progressive familial intrahepatic cholestasis patients with high serum gamma glutamyltranspeptidase have mutations in the gene (PGY3) coding for the MDR3 protein, a canalicular ATP-dependent phopshatidylcholine translocator. Recurrent intrahepatic cholestasis (previously benign recurrent cholestasis), is also linked to specific mutations in the FIC1 gene. Finally, in Alagille syndrome, mutations in the JAG1 gene cause deficiency Jagged 1, a ligand for Notch 1, a receptor determining cell fate during early embryogenesis. Diagnosis of Alagille syndrome, a condition that should be suspected in all patients with unexplained cholestasis, will thus be confirmed by genetic analysis for mutations of JAG1. In children with cholestasis and low serum bile acid levels, an inborn error of bile acid synthesis should be excluded by urinary bile acid analysis by means of fast atom bombardment-ionization mass-spectrometry. In contrast, in children with cholestasis and high serum bile acid concentrations, a high serum gamma glutamyltranspeptidase value would indicate MDR3 deficiency, which should be excluded through biliary phospholipid determination and genetic analysis of PGY3 gene. Finally, in those children with cholestasis, high serum bile acids and low gamma glutamyltranspeptidase activity, analysis of mutation in FIC1 and bile salt export pump genes may lead to the diagnosis of progressive familial intrahepatic cholestasis either from bile salt export pump or FIC1 deficiency.     

A new ABCB11 mutation in two Italian children with familial intrahepatic cholestasis

Progressive familial intrahepatic cholestasis (PFIC) syndromes are characterized by defects in transporters of conjugated bile acids into the bile canaliculus. Three genes (ATP8B1, ABCB11, ABCB4) are associated with the different forms, but no easy genotype–phenotype correlations help in the prioritization for gene testing. We developed a denaturing high-performance liquid chromatography (DHPLC) method to screen patients with PFIC for mutations in ATP8B1 and ABCB11, and combined genetic analyses with immunolabeling in liver for the ABCB11 and ABCB4 gene products. Used in combination with commercially available antibodies on liver specimens, the DHPLC approach allowed us to confirm the clinical diagnosis in two Italian sisters and to identify a novel missesnse mutation in ABCB11. Our findings are expected to facilitate detection of the molecular cause of PFIC in affected families.     

Cholestatic liver diseases: slow progress in understanding and treating slowly progressive disorders

BACKGROUND: Cholestatic liver diseases are characterized by failure of normal amounts of physiological bile to reach the gastrointestinal tract. Any interference with normal bile flow from the canalicular membrane of the hepatocyte to the distal common bile duct may result in cholestasis. METHODS: Literature review. RESULTS: In primary biliary cirrhosis (PBC), the small intrahepatic bile ducts are destructed, resulting in obstruction of intrahepatic bile flow, whereas extrahepatic and/or intrahepatic biliary strictures block the passage of bile towards the intestine in primary sclerosing cholangitis (PSC). In contrast, the biliary tree is morphologically unaffected in less common cholestatic liver diseases as benign recurrent intrahepatic cholestasis (BRIC) and progressive familiar intrahepatic cholestasis (PFIC1-4). Genetic defects in hepatic canalicular transport mechanisms and bile salt synthesis deficiencies seem to underlie these types of cholestatic disorders. CONCLUSION: Recent advances in understanding and treatment of cholestatic liver diseases may help in better diagnosing and treating the various conditions characterized by cholestasis.     

Progressive familial intrahepatic cholestasis: genetic disorders of biliary transporters

Progressive familial intrahepatic cholestasis types 1, 2 and 3 are childhood diseases of the liver. Benign recurrent intrahepatic cholestasis is predominantly an adult form with similar clinical symptoms that spontaneously resolve. These genetic disorders have significantly helped to unravel the basic mechanisms of the canalicular bile transport processes. Progressive familial intrahepatic cholestasis type 1 involves a gene also linked to benign recurrent intrahepatic cholestasis. The gene codes for an aminophospholipid translocase protein that maintains the integrity of the membrane. How a mutation in this protein causes cholestasis is unknown but is thought to involve the enterohepatic recirculation of bile acids. Progressive familial intrahepatic cholestasis types 2 and 3 involve the canalicular bile salt export pump and a phospholipid translocase, respectively, both of which are fundamental to bile secretion. This review covers the clinical manifestations, genetics, treatment and mechanism of each disease.