Novel ABCB4 mutations in an infertile female with progressive familial intrahepatic cholestasis type 3:A case report

BACKGROUND Mutations that occur in the ABCB4 gene,which encodes multidrug-resistant protein 3,underlie the occurrence of progressive familial intrahepatic cholestasis type 3(PFIC3).Clinical signs of intrahepatic cholestasis due to gene mutations typically first appear during infancy or childhood.Reports of PFIC3 occurring in adults are rare.CASE SUMMARY This is a case study of a 32-year-old infertile female Chinese patient with a 15-year history of recurrent abnormal liver function.Her primary clinical signs were elevated levels of alkaline phosphatase andγ-glutamyl transpeptidase.Other possible reasons for liver dysfunction were eliminated in this patient,resulting in a diagnosis of PFIC3.The diagnosis was confirmed using gene detection and histological analyses.Assessments using genetic sequencing analysis indicated the presence of two novel heterozygous mutations in the ABCB4 gene,namely,a 2950C>T;p.A984V mutation(exon 24)and a 667A>G;p.I223V mutation(exon 7).After receiving ursodeoxycholic acid(UDCA)treatment,the patient's liver function indices improved,and she successfully became pregnant by in vitro fertilization.However,the patient developed intrahepatic cholestasis of pregnancy in the first trimester.Fortunately,treatment with UDCA was safe and effective.CONCLUSION These novel ABCB4 heterozygous mutations have a variety of clinical phenotypes.Continued follow-up is essential for a comprehensive understanding of PFIC3.

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 inATP8B1.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.

Partial external biliary diversion in bile salt export pump deficiency: Association between outcome and mutation

To investigate the relation of two different mutations to the outcome of partial external biliary diversion (PEBD) in severe bile salt export pump (BSEP) deficiency. METHODSMutations in the gene encoding BSEP leading to severe BSEP deficiency in two unrelated patients were identified by genomic sequencing. Native liver biopsies and transiently transfected human embryonic kidney (HEK) 293 cells expressing either wild-type or mutated BSEP were subjected to immunofluorescence analysis to assess BSEP transporter localization. Bile acid profiles of patient and control bile samples were generated by ultra-performance liquid chromatography-tandem mass spectrometry. Wild-type and mutant BSEP transport of [3H]-labeled taurocholate (TC) and taurochenodeoxycholate (TCDC) was assessed by vesicular transport assays. RESULTSA girl (at 2 mo) presented with pruritus, jaundice and elevated serum bile salts (BS). PEBD stabilized liver function and prevented liver transplantation. She was heterozygous for the BSEP deletion p.T919del and the nonsense mutation p.R1235X. At the age of 17 years relative amounts of conjugated BS in her bile were normal, while total BS were less than 3% as compared to controls. An unrelated boy (age 1.5 years) presenting with severe pruritus and elevated serum BS was heterozygous for the same nonsense and another missense mutation, p.G1032R. PEBD failed to alleviate pruritus, eventually necessitating liver transplantation. BS concentration in bile was about 5% of controls. BS were mainly unconjugated with an unusual low amount of chenodeoxycholate derivatives (< 5%). The patients’ native liver biopsies showed canalicular BSEP expression. Both BSEP p.T919del and p.G1032R were localized in the plasma membrane in HEK293 cells. In vitro transport assays showed drastic reduction of transport by both mutations. Using purified recombinant BSEP as quantifiable reference, per-molecule transport rates for TC and TCDC were determined to be 3 and 2 BS molecules per wild-type BSEP transporter per minute, respectively. CONCLUSIONIn summary, our findings suggest that residual function of BSEP as well as substrate specificity influence the therapeutic effectiveness of PEBD in progressive familial intrahepatic cholestasis type 2 (PFIC-2).