Two Cases of Progressive Familial Intrahepatic Cholestasis Type 2: Role of Surgery with Brief Review of Literature.

Progressive familial intrahepatic cholestasis (PFIC) is a rare bile acid transporter defect and autosomal recessive disorder with type 2 being the most common type. Partial internal or external biliary diversion delays its progression to end-stage liver disease. Here, we discuss two cases of type 2 PFIC.

Liver transcript analysis reveals aberrant splicing due to silent and intronic variations in the ABCB11 gene.

BACKGROUND: Progressive familial intrahepatic cholestasis type 2 (PFIC2) is an autosomal recessive disease due to mutations in ABCB11. ABCB11 encodes the bile salt export pump (BSEP), the major transporter responsible for biliary bile acid secretion, which expression is restricted to hepatocytes. In some patients, molecular analysis of ABCB11 revealed either exonic or intronic variations - including common polymorphisms - predicted to affect splicing according to in silico analysis or in vitro minigene studies. Transcript analysis in liver tissue is the best way to determine whether the variations predicted to affect splicing are deleterious or not. METHODS AND RESULTS: We performed ABCB11 transcript analysis in liver tissue from five PFIC2 patients who had variations which were predicted to either affect splicing or not. Among eleven variants tested, only the silent c.3003A>G variant and the intronic c.3213+4A>G variant led to abnormal splicing as suggested by in silico analysis. CONCLUSION: ABCB11 liver transcript analysis is a useful tool to confirm or invalidate the predicted splicing effect of a silent or intronic ABCB11 variation.

Cell-based BSEP trans-inhibition: A novel, non-invasive test for diagnosis of antibody-induced BSEP deficiency.

Background & Aims: Antibody-induced bile salt export pump deficiency (AIBD) is an acquired form of intrahepatic cholestasis, which may develop following orthotopic liver transplantation (OLT) for progressive familial intrahepatic cholestasis type 2 (PFIC-2). Approximately 8-33% of patients with PFIC-2 who underwent a transplant develop bile salt export pump (BSEP) antibodies, which trans-inhibit this bile salt transporter from the extracellular, biliary side. AIBD is diagnosed by demonstration of BSEP-reactive and BSEP-inhibitory antibodies in patient serum. We developed a cell-based test directly measuring BSEP trans-inhibition by antibodies in serum samples to confirm AIBD diagnosis. Methods: Sera from healthy controls and cholestatic non-AIBD or AIBD cases were tested (1) for anticanalicular reactivity by immunofluorescence staining of human liver cryosections, (2) for anti-BSEP reactivity by immunofluorescence staining of human embryonic kidney 293 (HEK293) cells expressing BSEP-enhanced yellow fluorescent protein (EYFP) and immunodetection of BSEP-EYFP on Western blot, and (3) for BSEP trans-inhibition using HEK293 cells stably expressing Na+/taurocholate cotransporting polypeptide (NTCP)-mCherry and BSEP-EYFP. The trans-inhibition test uses [3H]-taurocholate as substrate and is divided into an uptake phase dominated by NTCP followed by BSEP-mediated export. For functional analysis, sera were bile salt depleted. Results: We found BSEP trans-inhibition by seven sera containing anti-BSEP antibodies, but not by five cholestatic or nine control sera, all lacking BSEP reactivity. Prospective screening of a patient with PFIC-2 post OLT showed seroconversion to AIBD, and the novel test method allowed monitoring of treatment response. Notably, we identified a patient with PFIC-2 post OLT with anti-BSEP antibodies yet without BSEP trans-inhibition activity, in line with asymptomatic presentation at serum sampling. Conclusions: Our cell-based assay is the first direct functional test for AIBD and allows confirmation of diagnosis as well as monitoring under therapy. We propose an updated workflow for AIBD diagnosis including this functional assay. Impact and Implications: Antibody-induced BSEP deficiency (AIBD) is a potentially serious complication that may affect patients with PFIC-2 after liver transplantation. To improve its early diagnosis and thus immediate treatment, we developed a novel functional assay to confirm AIBD diagnosis using a patient's serum and propose an updated diagnostic algorithm for AIBD.

Genotype-phenotype relationships of truncating mutations, p.E297G and p.D482G in bile salt export pump deficiency.

Background & Aims: Bile salt export pump (BSEP) deficiency frequently necessitates liver transplantation in childhood. In contrast to two predicted protein truncating mutations (PPTMs), homozygous p.D482G or p.E297G mutations are associated with relatively mild phenotypes, responsive to surgical interruption of the enterohepatic circulation (siEHC). The phenotype of patients with a compound heterozygous genotype of one p.D482G or p.E297G mutation and one PPTM has remained unclear. We aimed to assess their genotype-phenotype relationship. Methods: From the NAPPED database, we selected patients with homozygous p.D482G or p.E297G mutations (BSEP1/1; n = 31), with one p.D482G or p.E297G, and one PPTM (BSEP1/3; n = 30), and with two PPTMs (BSEP3/3; n = 77). We compared clinical presentation, native liver survival (NLS), and the effect of siEHC on NLS. Results: The groups had a similar median age at presentation (0.7-1.3 years). Overall NLS at age 10 years was 21% in BSEP1/3 vs. 75% in BSEP1/1 and 23% in BSEP3/3 (p <0.001). Without siEHC, NLS in the BSEP1/3 group was similar to that in BSEP3/3, but considerably lower than in BSEP1/1 (at age 10 years: 38%, 30%, and 71%, respectively; p = 0.003). After siEHC, BSEP1/3 and BSEP3/3 were associated with similarly low NLS, while NLS was much higher in BSEP1/1 (10 years after siEHC, 27%, 14%, and 92%, respectively; p <0.001). Conclusions: Individuals with BSEP deficiency with one p.E297G or p.D482G mutation and one PPTM have a similarly severe disease course and low responsiveness to siEHC as those with two PPTMs. This identifies a considerable subgroup of patients who are unlikely to benefit from interruption of the enterohepatic circulation by either surgical or ileal bile acid transporter inhibitor treatment. Impact and implications: This manuscript defines the clinical features and prognosis of individuals with BSEP deficiency involving the combination of one relatively mild and one very severe BSEP deficiency mutation. Until now, it had always been assumed that the mild mutation would be enough to ensure a relatively good prognosis. However, our manuscript shows that the prognosis of these patients is just as poor as that of patients with two severe mutations. They do not respond to biliary diversion surgery and will likely not respond to the new IBAT (ileal bile acid transporter) inhibitors, which have recently been approved for use in BSEP deficiency.

Antisense oligonucleotides rescue an intronic splicing variant in the ABCB11 gene that causes progressive familial intrahepatic cholestasis type 2.

BACKGROUND: Progressive familial intrahepatic cholestasis type 2 (PFIC2) is a rare disorder caused by variants in the ABCB11 gene encoding the bile salt export pump (BSEP). We investigated the molecular defect in a PFIC2 infant and rescued the splicing defect with antisense oligonucleotides (ASOs). METHODS: Whole-exome sequencing (WES) revealed compound heterozygous variants in the ABCB11 gene in a PFIC2 patient. Liver biopsy was immunostained for BSEP. The splicing effect of the candidate variants was investigated by minigene assay. ASOs were designed to rescue aberrant splicing. RESULTS: A Chinese girl of two nonconsanguineous healthy parents suffered from low glutamyl transpeptidase cholestasis and showed no response to the ursodeoxycholic acid. WES revealed that the patient was compound heterozygous for two novel variants in the ABCB11 gene: c.76+29T>G and c.390-2A>G. Liver immunohistochemistry showed the absence of BSEP. The variant c.76+29T>G was confirmed to retain 42 bp in the mature mRNA. The variant c.390-2A>G was confirmed to cause exon 6 skipping. We designed two ASOs and identified one of them that efficiently induced pseudoexon exclusion. CONCLUSION: We reported two novel variants of the ABCB11 gene, c.76+29T>G and c.390-2A>G, in a PFIC2 infant, thereby expanding the genotype of PFIC2. Our findings provide evidence for ASOs as a therapeutic approach for PFIC2 patients carrying intronic variants.

Progressive Familial Intrahepatic Cholestasis Type 2 in an Indian Child.

Progressive familial intrahepatic cholestasis (PFIC) is a chronic cholestasis syndrome that begins in infancy and usually progresses to cirrhosis within the first decade of life. There are three varieties of PFIC described: PFIC-1 occurs due to mutations in the ATP8B1 gene mapped to 18q21.31, PFIC-2 due to mutations in ABCB11 mapped to 2q24, and PFIC-3 due to mutations in ABCB4 located on 7q21.12. We report an Indian child whose mutation analysis was suggestive of PFIC-2. He underwent a biliary diversion at 3½ years of age but subsequently died secondary to massive hematemesis.

Bipolar and Related Disorders Induced by Sodium 4-Phenylbutyrate in a Male Adolescent with Bile Salt Export Pump Deficiency Disease.

Bile Salt Export Pump (BSEP) Deficiency disease, including Progressive Familial Intrahepatic Cholestasis type 2 (PFIC2), is a rare disease, usually leading within the first ten years to portal hypertension, liver failure, hepatocellular carcinoma. Often liver transplantation is needed. Sodium 4-phenylbutyrate (4-PB) seems to be a potential therapeutic compound for PFIC2. Psychiatric side effects in the adolescent population are little known and little studied since the drug used to treat children and infants. So we described a case of Caucasian boy, suffering from a late onset PFIC2, listed for a liver transplant when he was sixteen and treated with 4-FB (200 mg per kilogram of body weight per day). The drug was discontinued for the onset of bipolar and related disorders. This case illustrates possible psychiatric side effects of the drug.

Hepatocellular Carcinoma in a Boy with Progressive familial Intrahepatic Cholestasis Type II: Challenging Identification: Case report.

Hepatocellular carcinoma (HCC) is rare in children. Progressive familial intrahepatic cholestasis type II (PFIC2 and also called BSEP ((Bile Salt Export Pump)) deficiency) is an inherited disease that initiates end-stage liver cirrhosis which can predispose to HCC. HCC can occur in 15% of patients with PFIC2. In this case report, an 11-month-old boy with PFIC 2 was admitted for liver transplant work up. The finding of HCC was made incidentally by histopathology on the explanted liver after suspiciously gross examination. In this article, we found that the radiology (US) alone is not enough to exclude HCC. Finally, we conclude that any case of PFIC 2 (male or female) needs routine screening of serum AFP concentration, advanced radiological examination (CT, MRI) as well as careful macroscopic examination of their explanted liver (triple assessment) to exclude HCC.

Identification of a primary biliary cirrhosis associated protein as lysosome-associated membrane protein-2.

Primary biliary cirrhosis (PBC) is a chronic cholestatic liver disease of unknown etiology and abnormality of hepatobiliary transport might contribute to its pathogenesis. In this study, we aimed to isolate and identify new molecules associated with PBC. With hepatocyte canalicular membrane vesicles (CMVs) of PBC patients as immunogens, we screened the monoclonal antibody 1F9 (mAb1F9), whose antigen dominantly recognized the subapical domains in hepatocytes in normal livers. Immunohistochemistry revealed that the expression of mAb1F9 antigen (mAb1F9-Ag) significantly increased in PBC livers compared with control groups including normal livers, cirrhosis or cholestasis other than PBC. Interestingly, the augmented expression of mAb1F9-Ag was correlated with the severity of PBC, and ursodeoxycholic acid treatment may significantly improve the recovery of mAb1F9-Ag. In addition, redistribution of mAb1F9-Ag was found in 46% of PBC. mAb1F9-Ag was isolated and analyzed with mass spectrometry, which indicated lysosome-associated membrane protein 2 (LAMP-2) as the candidate. Further studies showed that mAb1F9 recognized LAMP-2 immunoprecipitates and vice verse, mAb1F9 reacted with recombinant LAMP-2. mAb1F9 and LAMP-2 antibody exhibited similar staining pattern and displayed similar subcellular localization. Together, the identity of mAb1F9-Ag is LAMP-2, suggesting that LAMP-2 may assist in the differentiation of PBC and predict a poor outcome in patients with PBC. BIOLOGICAL SIGNIFICANCE: This manuscript describes the expression of a specific antibody, named mAb1F9. The antigen recognized by mAb1F9 may assist in the differentiation of primary biliary cirrhosis (PBC) and predict a poor outcome in patients with PBC. Through antigen identification, we confirm the identity of mAb1F9-Ag as lysosome-associated membrane protein 2 (LAMP-2). The clinical relevance of the manuscript is well regarded since markers are rare and usually not successful for PBC diagnosis and treatment.

Orthotopic liver transplantation in a pediatric patient with progressive intrahepatic cholestasis: a coordinated perioperative subspecialty approach.

This report discusses the perioperative anesthesia management of a pediatric patient with end-stage liver disease from progressive intrahepatic cholestasis, with particular emphasis on the coordinated, multidisciplinary approach our institution uses.