Update on progressive familial intrahepatic cholestasis

Emerging drugs for the treatment of progressive familial intrahepatic cholestasis: a focus on phase II and III trials

INTRODUCTION

Progressive familial intrahepatic cholestasis (PFIC) is a group of disorders characterized by inappropriate bile formation, causing hepatic accumulation of bile acids and, subsequently, liver injury. Until recently, no approved treatments were available for these patients.

AREAS COVERED

Recent clinical trials for PFIC treatment have focused on intestine-restricted ileal bile acid transporter (IBAT) inhibitors. These compounds aim to reduce the pool size of bile acids by interrupting their enterohepatic circulation. Other emerging treatments in the pipeline include systemic IBAT inhibitors, synthetic bile acid derivatives, compounds targeting bile acid synthesis via the FXR/FGF axis, and chaperones/potentiators that aim to enhance the residual activity of the mutated transporters.

EXPERT OPINION

Substantial progress has been made in drug development for PFIC patients during the last couple of years. Although data concerning long-term efficacy are as yet only scarcely available, new therapies have demonstrated robust efficacy in a considerable fraction of patients at least on the shorter term. However, a substantial fraction of PFIC patients do not respond to these novel therapies and thus still requires surgical treatment, including liver transplantation before adulthood. Hence, there is still an unmet medical need for long-term effective medical, preferably non-surgical, treatment for all PFIC patients.

Impact of non-alcoholic fatty liver disease (NAFLD) and non-alcoholic steatohepatitis (NASH) on the expression and function of hepatobiliary transporters: A comprehensive mechanistic review

The liver plays a central role in the biotransformation and disposition of endogenous molecules and xenobiotics. In addition to drug-metabolizing enzymes, transporter proteins are key determinants of drug hepatic clearance. Hepatic transporters are transmembrane proteins that facilitate the movement of chemicals between sinusoidal blood and hepatocytes. Other drug transporters translocate molecules from hepatocytes into bile canaliculi for biliary excretion. The formers are known as basolateral, while the latter are known as canalicular transporters. Also, these transporters are classified into two super-families, the solute carrier transporter (SLC) and the adenosine triphosphate (ATP)-binding cassette (ABC) transporter. The expression and function of transporters involve complex regulatory mechanisms, which are contributing factors to interindividual variability in drug pharmacokinetics and disposition. A considerable number of liver diseases are known to alter the expression and function of drug transporters. Among them, non-alcoholic fatty liver disease (NAFLD) is a chronic condition with a rapidly increasing incidence worldwide. NAFLD, recently reclassified as metabolic dysfunction-associated steatotic liver disease (MASLD), is a disease continuum that includes steatosis with or without mild inflammation (NASH), and potentially neuroinflammatory pathology. NASH is additionally characterized by the presence of hepatocellular injury. During NAFLD and NASH, drug transporters exhibit altered expression and function, leading to altered drug pharmacokinetics and pharmacodynamics, thus increasing the risk of adverse drug reactions. The purpose of the present review is to provide comprehensive mechanistic information on the expression and function of hepatic transporters under fatty liver conditions and hence, the impact on the pharmacokinetic profiles of certain drugs from the available pre-clinical and clinical literature.

An Approach to Investigations of Chronic Liver Disease

Chronic liver disease (CLD) in children is more diverse compared to adults with respect to the etiology, progression and response to therapy. After history and clinical examination, the first step is to confirm the presence of CLD with basic blood investigations and ultrasonography. Markers of portal hypertension are splenomegaly, increased portal vein diameter, thrombocytopenia and presence of varices on endoscopy. The next step is to evaluate the etiology of CLD which will depend on the age of the child and needs targeted investigations as metabolic and inherited causes predominate in early childhood. CLD progression ought to be monitored regularly and several non-invasive markers are available but they have to be evaluated further in children. Since CLD progresses, complications have to be detected early not only to initiate appropriate treatment but also to prognosticate.

Protocols of Investigation of Neonatal Cholestasis-A Critical Appraisal

Neonatal cholestasis (NC) starts during the first three months of life and comprises extrahepatic and intrahepatic groups of diseases, some of which have high morbimortality rates if not timely identified and treated. Prolonged jaundice, clay-colored or acholic stools, and choluria in an infant indicate the urgent need to investigate the presence of NC, and thenceforth the differential diagnosis of extra- and intrahepatic causes of NC. The differential diagnosis of NC is a laborious process demanding the accurate exclusion of a wide range of diseases, through the skillful use and interpretation of several diagnostic tests. A wise integration of clinical-laboratory, histopathological, molecular, and genetic evaluations is imperative, employing extensive knowledge about each evaluated disease as well as the pitfalls of each diagnostic test. Here, we review the difficulties involved in correctly diagnosing the cause of cholestasis in an affected infant.

Overview of Progressive Familial Intrahepatic Cholestasis

Bile acid transport is a complex physiologic process, of which disruption at any step can lead to progressive intrahepatic cholestasis (PFIC). The first described PFIC disorders were originally named as such before identification of a genetic cause. However, advances in clinical molecular genetics have led to the identification of additional disorders that can cause these monogenic inherited cholestasis syndromes, and they are now increasingly referred to by the affected protein causing disease. The list of PFIC disorders is expected to grow as more causative genes are discovered. Here forth, we present a comprehensive overview of known PFIC disorders.

Neurodevelopmental Outcomes in Children With Inherited Liver Disease and Native Liver

OBJECTIVE

To evaluate neurodevelopmental status among children with inherited cholestatic liver diseases with native liver and variables predictive of impairment.

METHODS

Participants with Alagille syndrome (ALGS), progressive familial intrahepatic cholestasis (PFIC), and alpha 1 antitrypsin deficiency (A1AT) enrolled in a longitudinal, multicenter study and completed the Wechsler Preschool and Primary Scale of Intelligence-III or Intelligence Scale for Children-IV. Full Scale Intelligence Quotient (FSIQ) was analyzed continuously and categorically (>100, 85-99, 70-84, <70). Univariate linear regression was performed to study association between FSIQ and risk factors, stratified by disease.

RESULTS

Two hundred and fifteen completed testing (ALGS n = 70, PFIC n = 43, A1AT n = 102); median age was 7.6 years (3.0-16.9). Mean FSIQ in ALGS was lower than A1AT (94 vs 101, P = 0.01). Frequency of FSIQ < 85 (>1 standard deviation [SD] below average) was highest in ALGS (29%) versus 18.6% in PFIC and 12.8% in A1AT, and was greater than expected in ALGS based on normal distribution (29% vs 15.9%, P = 0.003). ALGS scored significantly lower than test norms in almost all Wechsler composites; A1AT scored lower on Working Memory and Processing Speed; PFIC was not different from test norms. Total bilirubin, alkaline phosphatase, albumin, hemoglobin, and parental education were significantly associated with FSIQ.

CONCLUSIONS

Patients with ALGS are at increased risk of lower FSIQ, whereas our data suggest A1AT and PFIC are not. A1AT and ALGS appear vulnerable to working memory and processing speed deficits suggestive of attention/executive function impairment. Malnutrition, liver disease severity, and sociodemographic factors appear related to FSIQ deficits, potentially identifying targets for early interventions.

Liver transplantation in pediatric patients with progressive familial intrahepatic cholestasis: Single center experience of seven cases

Backgrounds/Aims

Progressive familial intrahepatic cholestasis (PFIC) is an autosomal recessive inherited disease requiring liver transplantation (LT). The objective of this study was to investigate the clinicopathological features and posttransplant courses of seven LT recipients with PFIC.

Methods

This was a retrospective single-center study of patients with PFIC who underwent LT from January 2013 to June 2020.

Results

Two and five patients were diagnosed with PFIC type 1 and type 2, respectively. For all seven patients, age of PFIC onset was at birth. Jaundice was present in all cases. Mean pretransplant total and direct bilirubin levels were 16.1 ± 8.1 mg/dL and 12.4 ± 6.2 mg/dL, respectively. Median patient age and body weight at LT were 10 months and 7 kg, respectively. Types of donors were mothers of patients in four and deceased donors in three. All five patients with PFIC type 2 recovered uneventfully. One patient each with PFIC type 1 underwent retransplantation due to graft failure or died due to multi-organ failure. Overall graft and patient survival rates at five years were 66.7% and 83.3%, respectively. Bile salt export pump immunohistochemical staining showed normal canalicular expression in two patients with PFIC type 1, focal loss in two patients with PFIC type 2, and total loss in three patients with PFIC type 2.

Conclusions

LT is currently the only effective treatment for PFIC-associated end-stage liver diseases. It is mandatory to perform regular follow-up due to the risk of complications including steatohepatitis, especially for patients with PFIC type 1.

Clinical Case of the Byler’s Syndrome in a Child

Прогрессирующий семейный внутрипеченочный холестаз (ПСВХ) – это редкая форма наследственной патологии печени, которая обусловлена дефектами секреции желчи, непрерывно прогрессирует и способствует формированию фиброза и цирроза печени. Частота данной патологии составляет 1 на 50 000–100 000 новорожденных. Начинается заболевание, как правило, в младенчестве, но прогрессирование процесса может быть и в подростковом возрасте. Выделяют три типа ПСВХ: при ПСВХ 1-го и 2-го типа нарушается секреция солей желчных кислот, а при ПСВХ 3-го типа изменена экскреция фосфолипидов. Диагностика основана на клинических проявлениях, результатах холангиографии, УЗИ, гистологии печени и специфических тестах. Терапия урсодезоксихолевой кислотой должна быть начата во всех случаях для предотвращения прогрессирования повреждения печени. Тем не менее, большинство пациентов с ПСВХ в конечном итоге являются кандидатами на трансплантацию печени. Таким образом, ранняя диагностика ПСВХ позволяет своевременно определять тактику ведения пациентов с целью предотвращения необратимого исхода заболевания.

Progressive familial intrahepatic cholestasis (PFIC) is a rare form of hereditary diseases of the liver, which (due to defects in bile secretion) constantly progresses and promotes the formation of liver fibrosis and cirrhosis. Its incidence is estimated as 1 to 50.000–100.000 newborns. The onset of the disease is generally in infancy, but the diagnosis may be delayed until adolescence. Three types of PFIC are distinguished: in PFIC types I, II, the secretion of bile salts deteriorates, whereas in PFIC type III, the excretion of phospholipids is altered. Diagnosis is based on clinical manifestations,cholangiography, liver ultrasonography, and histology, as well as on specific tests. Ursodeoxycholic acid therapy should be initiated in all patients to prevent the progression of liver damage. However, the majority of PFIC patients are ultimately candidates for liver transplantation. Thus, early diagnosis of PFIC allows timely determination of patient management tactics in order to prevent an irreversible outcome of the disease.

Ileal exclusion for pruritus treatment in children with progressive familial intrahepatic cholestasis and other cholestatic diseases

BACKGROUND

Pruritus is a major health-related quality-of-life burden in progressive familial intrahepatic cholestasis (PFIC) and other childhood cholestatic liver diseases. Several nontransplant surgical techniques were developed in an attempt to ameliorate symptoms and slow disease progression. Very few case-series have been published on a particular intervention, ileal exclusion (IE), which has been considered to be inferior to the other approaches.

METHODS

We conducted a single-center retrospective chart-review case-series of patients submitted to IE as the first-line surgical treatment at our institution from 1995 to 2018. The primary goal was pruritus relief, followed by survival with the native liver and improvement in biochemical parameters.

RESULTS

Eleven patients were submitted to IE, with a mean follow-up of 60 months. Complete resolution or significant reduction of pruritus was obtained in 72.7% (n = 8) of patients. One patient (9.1%) had a major postoperative complication that required surgery. No other morbidities were reported. Two cases progressed to end-stage liver disease (ESLD) within the short-term and one year after surgery.

CONCLUSIONS

This case series study shows that IE provided excellent results in pruritus control and permitted survival with the native liver. We believe IE is a safe procedure, with few associated morbidities, and should be considered more often as primary surgical treatment for PFIC and other cholestasis.

LEVEL OF EVIDENCE

IV.

Cholestasis in Benign Recurrent Intrahepatic Cholestasis 2

Benign recurrent intrahepatic cholestasis represents a rare class of autosomal recessive chronic cholestasis disorders, usually presenting with recurrent episodes of intense pruritus and jaundice. We report a 27-year-old woman presenting with benign recurrent intrahepatic cholestasis type 2 due to heterozygosity in ABCB11. Interestingly, she was also found to be heterozygous in cystic fibrosis transmembrane conductance regulator, NPHP4, and A1ATD (SERPINA1), which may explain the severe nature of her disease expression because heterozygosity in each of these genes has been associated with cholestasis. Finally, she exhibited a response to steroids that may have implications for future treatment of bile salt export pump-related diseases.

Phenotype-Genotype Correlation of North Indian Progressive Familial Intrahepatic Cholestasis type2 Children Shows p.Val444Ala and p.Asn591Ser Variants and Retained BSEP Expression

Backgrounds and Aims: Progressive familial intrahepatic cholestasis type 2 (PFIC2) is caused by a defect or deficiency of bile salt export protein (BSEP) due to mutation in the ABCB11 gene. We intend to evaluate the phenotype-genotype correlation in 10 diagnosed cases of PFIC2 in a single tertiary care center in North India. Methods: The clinical, biochemical, histopathological, immunohistochemical, ultrastructural and genetic data of the 10 diagnosed cases of PFIC2 were recorded. Results: Icterus, pruritus and bleeding manifestations were the commonest clinical symptoms. Giant cell transformation was seen in 50% of the patients. Two predominant genetic variants were ABCB11 missense p.Val444Ala (c. 1331 T > C) and ABCB11 missense p.Asn591Ser (c. 1772 A > G) in their homozygous or compound heterozygous states and were associated with retained BSEP immunopositivity and reduced but retained BSEP immunopositivity respectively. Conclusion: Retention of BSEP is common in North Indian children of PFIC2 with no phenotype-genotype correlation.

Successful Treatment with Rituximab and Immunoadsorption for an Auto-Antibody Induced Bile Salt Export Pump Deficiency in a Liver Transplanted Patient

We present an 8 years old girl who was diagnosed at 6 months of age of Progressive Familial Intrahepatic Cholestasis type 2. Although liver transplantation (LT) was classically considered curative for these patients, cholestasis recurrence with normal gamma-glutamyl transpeptidase (GGT), mediated by anti-bile salt export pump (BSEP) antibodies after LT (auto-antibody Induced BSEP Deficiency, AIBD) has been recently reported. Our patient underwent LT at 14 months. During her evolution, patient presented three episodes of acute rejection. Seven years after the LT, the patient presented pruritus with cholestasis and elevation of liver enzymes with persistent normal GGT. Liver biopsy showed intrahepatic cholestasis and giant-cell transformation with very low BSEP activity. Auto-antibodies against BSEP were detected therefore an AIBD was diagnosed. She was treated with Rituximab and immunoadsorption with resolution of the AIBD. As a complication of the treatment she developed a pneumocystis infection successfully treated with corticoids, cotrimoxazol and anidulafungin.

Danger of Herbal Tea: A Case of Acute Cholestatic Hepatitis Due to Artemisia annua Tea

Background:Artemisia annua is a Chinese medicinal herb. Artemisinin-derivatives are recommended as part of a combination treatment for uncomplicated malaria. Herbal and dietary supplements (HDS) are increasingly used worldwide and HDS-induced liver injury is becoming a growing concern.

Case Report: We present the first case of severe acute cholestatic hepatitis due to the intake of Artemisia annua tea as chemoprophylaxis for malaria in a patient returning from Ethiopia. The patients presented with jaundice, elevated transaminases, and parameters of cholestasis (total bilirubin 186.6 μmol/L, conjugated bilirubin 168.5 μmol/L). A liver biopsy showed a portal hepatitis with lymphocytic infiltration of the bile ducts and diffuse intra-canalicular and intra-cytoplasmic bilirubinostasis. The toxicologic analysis of the Artemisia tea revealed the ingredients arteannuin b, deoxyartemisin, campher, and scopoletin. There were no other identifiable etiologies of liver disease. The Roussel Uclaf Causality Assessment Method (RUCAM) score assessed a “probably” causal relationship. Sequencing of genes encoding for hepatic transporters for bile acid homeostasis (BSEP, MDR3, and FIC1) found no genetic variants typically associated with hereditary cholestasis syndromes. Normalization of bilirubin occurred 3 months after the onset of disease.

Conclusion: The use of artemisinin-derivatives for malaria prevention is ineffective and potentially harmful and should thus be discouraged. Moreover, the case demonstrates our as yet inadequate understanding of the pathophysiology and susceptibility to HDS induced liver injury.

Liver-directed gene therapy results in long-term correction of progressive familial intrahepatic cholestasis type 3 in mice

BACKGROUND & AIMS

Progressive familial intrahepatic cholestasis type 3 (PFIC3), for which there are limited therapeutic options, often leads to end-stage liver disease before adulthood due to impaired ABCB4-dependent phospholipid transport to bile. Using adeno-associated virus serotype 8 (AAV8)-mediated gene therapy, we aimed to restore the phospholipid content in bile to levels that prevent liver damage, thereby enabling stable hepatic ABCB4 expression and long-term correction of the phenotype in a murine model of PFIC3.

METHODS

Ten-week-old Abcb4-/- mice received a single dose of AAV8-hABCB4 (n = 10) or AAV8-GFP (n = 7) under control of a liver specific promoter via tail vein injection. Animals were sacrificed either 10 or 26 weeks after vector administration to assess transgene persistence, after being challenged with a 0.1% cholate diet for 2 weeks. Periodic evaluation of plasma cholestatic markers was performed and bile duct cannulation enabled analysis of biliary phospholipids. Liver fibrosis and the Ki67 proliferation index were assessed by immunohistochemistry.

RESULTS

Stable transgene expression was achieved in all animals that received AAV8-hABCB4 up to 26 weeks after administration. AAV8-hABCB4 expression restored biliary phospholipid excretion, increasing the phospholipid and cholesterol content in bile to levels that ameliorate liver damage. This resulted in normalization of the plasma cholestatic markers, alkaline phosphatase and bilirubin. In addition, AAV8-hABCB4 prevented progressive liver fibrosis and reduced hepatocyte proliferation for the duration of the study.

CONCLUSION

Liver-directed gene therapy provides stable hepatic ABCB4 expression and long-term correction of the phenotype in a murine model of PFIC3. Translational studies that verify the clinical feasibility of this approach are warranted.

LAY SUMMARY

Progressive familial intrahepatic cholestasis type 3 (PFIC3) is a severe genetic liver disease that results from impaired transport of lipids to bile, which makes the bile toxic to liver cells. Because therapeutic options are currently limited, this study aims to evaluate gene therapy to correct the underlying genetic defect in a mouse model of this disease. By introducing a functional copy of the missing gene in liver cells of mice, we were able to restore lipid transport to bile and strongly reduce damage to the liver. The proliferation of liver cells was also reduced, which contributes to long-term correction of the phenotype. Further studies are required to evaluate whether this approach can be applied to patients with PFIC3.

Progressive Familial Intrahepatic Cholestasis in Korea: A Clinicopathological Study of Five Patients

BACKGROUND

Progressive familial intrahepatic cholestasis (PFIC) is a heterogeneous group of autosomal recessive liver diseases that present as neonatal cholestasis. Little is known of this disease in Korea.

METHODS

The records of five patients histologically diagnosed with PFIC, one with PFIC1 and four with PFIC2, by liver biopsy or transplant were reviewed, and ATP8B1 and ABCB11 mutation status was analyzed by direct DNA sequencing. Clinicopathological characteristics were correlated with genetic mutations.

RESULTS

The first symptom in all patients was jaundice. Histologically, lobular cholestasis with bile plugs was the main finding in all patients, whereas diffuse or periportal cholestasis was identified only in patients with PFIC2. Giant cells and ballooning of hepatocytes were observed in three and three patients with PFIC2, respectively, but not in the patient with PFIC1. Immunostaining showed total loss of bile salt export pump in two patients with PFIC2 and focal loss in two. Lobular and portal based fibrosis were more advanced in PFIC2 than in PFIC1. ATP8B1 and ABCB11 mutations were identified in one PFIC1 and two PFIC2 patients, respectively. One PFIC1 and three PFIC2 patients underwent liver transplantation (LT). At age 7 months, one PFIC2 patient was diagnosed with concurrent hepatocellular carcinoma and infantile hemangioma in an explanted liver. The patient with PFIC1 developed steatohepatitis after LT. One patient showed recurrence of PFIC2 after 10 years and underwent LT.

CONCLUSIONS

PFIC is not rare in patients with neonatal cholestasis of unknown origin. Proper clinicopathologic correlation and genetic testing can enable early detection and management.

Familial intrahepatic cholestasis: New and wide perspectives

BACKGROUND

Progressive familial intrahepatic cholestasis (PFIC) includes autosomal recessive cholestatic rare diseases of childhood.

AIMS

To update the panel of single genes mutations involved in familial cholestasis.

METHODS

PubMed search for "familial intrahepatic cholestasis" alone as well as in combination with other key words was performed considering primarily original studies and meta-analyses.

RESULTS

PFIC1 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.

CONCLUSION

There 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.

Quality of Life in Patients With Progressive Familial Intrahepatic Cholestasis: No Difference Between Post-liver Transplantation and Post-partial External Biliary Diversion

OBJECTIVES

In patients with progressive familial intrahepatic cholestasis (PFIC), partial external biliary diversion (PEBD), which is associated with a permanent stoma, is recommended as first-line therapy, whereas primary liver transplantation (LTx) is restricted to those with cirrhosis. Our aim was to quantify the health-related quality of life (HRQOL) in patients with PFIC and to evaluate whether there is a difference in their HRQOL depending on the surgical approach.

METHODS

A prospective HRQOL study on a consecutive series of PFIC was conducted using Pediatric Quality of Life Inventory 4.0 child-self and parent-proxy reports. Patients with PFIC after PEBD who still lived with their native livers were compared to those after LTx. Both groups were compared to healthy children.

RESULTS

A total of 32 patients (53% girls) patients with a mean age of 17.7 ± 7.3 years were studied. Twenty-two had undergone LTx at a mean age of 7.8 ± 3.8 years and 10 had undergone PEBD at a mean age of 4.1 ± 3.9 years. At the time of HRQOL assessment, the mean age was 18.9 ± 7.5 years in the LTx group and 15.3 ± 6.5 years in the PEBD group. Child-self and parent-proxy reports showed no significant difference in HRQOL between patients with PFIC after LTx and those after PEBD except for marginal difference in physical functioning/health (P = 0.07). Except for a lower score in patient school functioning of patients after LTx (P = 0.01), HRQOL-results showed no difference from healthy children in any group.

CONCLUSIONS

The HRQOL of patients with PFIC after PEBD was similar to those after LTx. The HRQOL in both groups was also similar to that of healthy children. Thus, our data support the current policy of PEBD as primary surgical treatment for patients with PFIC without cirrhosis.

Cryptogenic cholestasis in young and adults: ATP8B1, ABCB11, ABCB4, and TJP2 gene variants analysis by high-throughput sequencing

BACKGROUND

Mutations in ATP-transporters ATPB81, ABCB11, and ABCB4 are responsible for progressive familial intrahepatic cholestasis (PFIC) 1, 2 and 3, and recently the gene for tight junction protein-2 (TJP2) has been linked to PFIC4.

AIM

As these four genes have been poorly studied in young people and adults, we investigated them in this context here.

METHODS

In patients with cryptogenic cholestasis, we analyzed the presence of mutations by high-throughput sequencing. Bioinformatics analyses were performed for mechanistic and functional predictions of their consequences on biomolecular interaction interfaces.

RESULTS

Of 108 patients, 48 whose cause of cholestasis was not established were submitted to molecular analysis. Pathogenic/likely pathogenic mutations were found in ten (21%) probands for 13 mutations: two in ATP8B 1, six in ABCB11, two in ABCB4, three in TJP2. We also identified seven variants of uncertain significance: two in ATP8B1, one in ABCB11, two in ABCB4 and two in TJP2. Finally, we identified 11 benign/likely benign variants. Patients with pathogenic/likely pathogenic mutations had higher levels of liver stiffness (measured by FibroScan®) and bile acids, as well as higher rates of cholestatic histological features, compared to the patients without at least likely pathogenic mutations. The multivariate analysis showed that itching was the only independent factor associated with disease-causing mutations (OR 5.801, 95% CI 1.244-27.060, p = 0.025).

CONCLUSIONS

Mutations in the genes responsible for PFIC may be involved in both young and adults with cryptogenic cholestasis in a considerable number of cases, including in heterozygous status. Diagnosis should always be suspected, particularly in the presence of itching.

Obeticholic acid, a selective farnesoid X receptor agonist, regulates bile acid homeostasis in sandwich-cultured human hepatocytes

Farnesoid X receptor (FXR) is a master regulator of bile acid homeostasis through transcriptional regulation of genes involved in bile acid synthesis and cellular membrane transport. Impairment of bile acid efflux due to cholangiopathies results in chronic cholestasis leading to abnormal elevation of intrahepatic and systemic bile acid levels. Obeticholic acid (OCA) is a potent and selective FXR agonist that is 100‐fold more potent than the endogenous ligand chenodeoxycholic acid (CDCA). The effects of OCA on genes involved in bile acid homeostasis were investigated using sandwich‐cultured human hepatocytes. Gene expression was determined by measuring mRNA levels. OCA dose‐dependently increased fibroblast growth factor‐19 (FGF‐19) and small heterodimer partner (SHP) which, in turn, suppress mRNA levels of cholesterol 7‐alpha‐hydroxylase (CYP7A1), the rate‐limiting enzyme for de novo synthesis of bile acids. Consistent with CYP7A1 suppression, total bile acid content was decreased by OCA (1 μmol/L) to 42.7 ± 20.5% relative to control. In addition to suppressing de novo bile acids synthesis, OCA significantly increased the mRNA levels of transporters involved in bile acid homeostasis. The bile salt excretory pump (BSEP), a canalicular efflux transporter, increased by 6.4 ± 0.8‐fold, and the basolateral efflux heterodimer transporters, organic solute transporter α (OST_α) and OST_β increased by 6.4 ± 0.2‐fold and 42.9 ± 7.9‐fold, respectively. The upregulation of BSEP and OST_α and OST_β, by OCA reduced the intracellular concentrations of d₈‐TCA, a model bile acid, to 39.6 ± 8.9% relative to control. These data demonstrate that OCA does suppress bile acid synthesis and reduce hepatocellular bile acid levels, supporting the use of OCA to treat bile acid‐induced toxicity observed in cholestatic diseases.

Clinical Variability After Partial External Biliary Diversion in Familial Intrahepatic Cholestasis 1 Deficiency

OBJECTIVES

Familial intrahepatic cholestasis 1 (FIC1) deficiency is caused by a mutation in the ATP8B1 gene. Partial external biliary diversion (PEBD) is pursued to improve pruritus and arrest disease progression. Our aim is to describe clinical variability after PEBD in FIC1 disease.

METHODS

We performed a single-center, retrospective review of genetically confirmed FIC1 deficient patients who received PEBD. Clinical outcomes after PEBD were cholestasis, pruritus, fat-soluble vitamin supplementation, growth, and markers of disease progression that included splenomegaly and aspartate aminotransferase-to-platelet ratio index.

RESULTS

Eight patients with FIC1 disease and PEBD were included. Mean follow-up was 32 months (range 15-65 months). After PEBD, total bilirubin was <2 mg/dL in all patients at 8 months after surgery, but 7 of 8 subsequently experienced a total of 15 recurrent cholestatic events. Subjective assessments of pruritus demonstrated improvement, but itching exacerbation occurred during cholestatic episodes. High-dose fat-soluble vitamin supplementation persisted, with increases needed during cholestatic episodes. Weight z scores improved (-3.4 to -1.65, P < 0.01). Splenomegaly did not worsen or develop and 1 patient developed an aminotransferase-to-platelet ratio index score of >0.7 suggesting development of fibrosis 24 months after PEBD.

CONCLUSIONS

Clinical variability is evident among genetically defined FIC1 deficient patients after PEBD, even among those with identical mutations. Recurrent, self-limited episodes of cholestasis and pruritus are reminiscent of the benign recurrent intrahepatic cholestasis phenotype. Despite diversion of bile from the intestinal lumen, weight gain improved while fat-soluble vitamin requirements persisted. Significant progression of liver disease was not evident during follow-up.

Rare ER protein misfolding-mistrafficking disorders: Therapeutic developments

The presence of a functional protein at the appropriate location in the cell is the result of the processes of transcription, translation, folding and trafficking to the correct destination. There are numerous diseases that are caused by protein misfolding, mainly due to mutations in the respective gene. The consequences of this misfolding may be that proteins effectively lose their function, either by being removed by the cellular quality control machinery or by accumulating at the incorrect intracellular or extracellular location. A number of mutations that lead to protein misfolding and affect trafficking to the final destination, e.g. Cystic fibrosis, Wilson's disease, and Progressive Familial Intrahepatic 1 cholestasis, result in proteins that retain partial function if their folding and trafficking is restored either by molecular or pharmacological means. In this review, we discuss several mutant proteins within this class of misfolding diseases and provide an update on the status of molecular and therapeutic developments and potential therapeutic strategies being developed to counter these diseases.

Molecular characterization of exons 6, 8 and 9 of ABCB4 gene in children with Progressive Familial Intrahepatic Cholestasis type 3

AIM OF WORK

To estimate the frequency of mutations involving exons 6, 8 and 9 of Adenosine triphosphate-binding cassette, subfamily B, member 4 (ABCB4) gene among children with progressive intrahepatic cholestasis with high γ-GT activity (PFIC3).

SUBJECTS AND METHODS

Cross sectional study was conducted on 30 children with PFIC3. Genotyping was performed by sequencing analysis of exons 6, 8 and exon 9 of ABCB4 gene.

RESULTS

Heterozygous synonymous polymorphic variant was detected in exon 6 (rs 1202283) and in exon 8 (rs 2109505). No mutations in studied exons were detected.

CONCLUSION

Exons 6, 8 and 9 mutations of ABCB4 gene are not common among Egyptian children with PFIC3.

Child with Jaundice and Pruritus: How to Evaluate?

Jaundice with pruritus is a manifestation of cholestasis. The defective biliary drainage causes accumulation of substances that are usually excreted in bile, which in turn causes pruritus. The exact nature of the pruritogen is under evaluation. However, lysophosphatidic acid is the current favourite. The causes of cholestasis can be broadly classified as intra or extrahepatic, with intrahepatic disorders being more often associated with pruritus. Cholestatic phase of acute viral hepatitis, progressive familial intrahepatic cholestasis, syndromic and non-syndromic paucity of intralobular bile ductules, drug induced cholestasis and sclerosing cholangitis (SC) are the common causes in children. An algorithmic approach facilitates early etiological diagnosis by careful clinical evaluation combined with investigations including gamma glutamyl transpeptidase, radiological imaging (ultrasonography, magnetic resonance cholangiopancreatography), liver biopsy and genetic analysis. Management is largely supportive and includes nutritional rehabilitation with supplement of fat soluble vitamins and calcium, stepwise therapy of pruritus with drugs (ursodeoxycholic acid, rifampicin, bile acid sequestrants and/or opioid antagonists) and biliary diversion surgery. Complications of advanced liver disease and portal hypertension need to be addressed. Liver transplantation is required in children with refractory pruritus affecting the quality of life or those with end stage liver disease. Relief of biliary obstruction by endoscopy or surgery and treatment of diseases associated with SC like histiocytosis may be rewarding. Long-term follow-up for development of complications of liver disease and hepatocellular/ cholangiocarcinoma is essential. Thus, an early diagnosis and stepwise treatment with an understanding of the pathogenesis of pruritus in cholestatic disorders may decrease morbidity and mortality.

Proteomic Analysis of the Rat Canalicular Membrane Reveals Expression of a Complex System of P4-ATPases in Liver

Transport processes in the canalicular membrane are key elements in bile formation and are the driving force of the enterohepatic circulation of bile salts. The canalicular membrane is constantly exposed to the detergent action of bile salts. One potential element protecting the canalicular membrane from the high canalicular bile salt concentrations may be bile salt resistant microdomains, however additional factors are likely to play a role. To obtain more insights into the molecular composition of the canalicular membrane, the proteome of highly purified rat canalicular membrane vesicles was determined. Isolated rat canalicular membrane vesicles were stripped from adhering proteins, deglycosylated and protease digested before subjecting the samples to shot gun proteomic analysis. The expression of individual candidates was studied by PCR, Western blotting and immunohistochemistry. A total of 2449 proteins were identified, of which 1282 were predicted to be membrane proteins. About 50% of the proteins identified here were absent from previously published liver proteomes. In addition to ATP8B1, four more P4-ATPases were identified. ATP8A1 and ATP9A showed expression specific to the canalicular membrane, ATP11C at the bLPM and ATP11A in an intracellular vesicular compartment partially colocalizing with RAB7A and EEA1 as markers of the endosomal compartment. This study helped to identify additional P4-ATPases from rat liver particularly in the canalicular membrane, previously not known to be expressed in liver. These P4-ATPases might be contributing for maintaining transmembrane lipid homeostasis in hepatocytes.

Clinical and ABCB11 profiles in Korean infants with progressive familial intrahepatic cholestasis

AIM: To investigate clinical profiles and mutations of ABCB11 in Koreans with progressive familial intrahepatic cholestasis 2 and review the differences between Koreans and others.

METHODS: Of 47 patients with neonatal cholestasis, five infants had chronic intrahepatic cholestasis with normal γ-glutamyl transpeptidase. Direct sequencing analyses of ABCB11, including exons and introns, were performed from peripheral blood.

RESULTS: Living donor-liver transplantation was performed in four patients because of rapidly progressive hepatic failure and hepatocellular carcinoma. Three missense mutations were found in two patients: compound heterozygous 677C>T (S226L)/3007G>A (G1003R) and heterozygous 2296G>A (G766R). The mutations were located near and in the transmembranous space.

CONCLUSION: Alterations in the transmembrane of the bile salt export pump in the Korean infants were different from those previously reported in Chinese, Japanease, Taiwanese, and European patients.

Increased frequency of double and triple heterozygous gene variants in children with intrahepatic cholestasis

AIM

Single gene mutations cause syndromes of intrahepatic cholestasis, but previous multi-gene mutation screening in children with idiopathic cholestasis failed to fulfill diagnostic criteria in approximately two-thirds of children. In adults with fibrosing cholestatic disease, heterozygous ABCB4 mutations were present in 34% of patients. Here, we hypothesized that children with idiopathic cholestasis have a higher frequency of heterozygous non-synonymous gene sequence variants.

METHODS

We analyzed the frequency and types of variants in 717 children in whom high-throughput sequencing of the genes SERPINA1, JAG1, ATP8B1, ABCB11 and ABCB4 was performed as part of an evaluation for idiopathic intrahepatic cholestasis cholestasis. The frequency of non-synonymous variants (NSV) was compared with those of 1092 control subjects enrolled in the 1000 Genome Project.

RESULTS

The frequency of NSV in single genes was similar between disease (25%) and controls (26%, P = 0.518). In contrast, double or triple NSV in two or more genes were more frequent in disease (n = 7%) than controls (n = 4.7%, P = 0.028). Detailed review of clinical and laboratory information in a subgroup of double or triple heterozygous patients revealed variable γ-glutamyltransferase levels and severity of pruritus, with liver biopsies showing stage 2-3 fibrosis.

CONCLUSION

Children with idiopathic intrahepatic cholestasis have a higher frequency of double or triple NSV in SERPINA1, JAG1, ATPB1, ABCB11 or ABCB4. These findings raise the potential role for gene-gene relationships in determining the phenotype of cholestatic liver disease in children.

Heterozygous ABCB4 mutations in children with cholestatic liver disease

BACKGROUND & AIMS

Monoallelic defects in ABCB4, which encodes the canalicular floppase for phosphatidylcholine MDR3, have been encountered in association with a variety of hepatobiliary disorders, particularly in adult subjects. In this study, we examined the presence of heterozygous ABCB4 variants in a cohort of children with chronic cholestasis and assessed the pathogenicity of the missense changes identified.

METHODS

Sixty-seven children with chronic liver dysfunction were studied by the sequencing of ABCB4 and multiplex ligation-dependent probe amplification analysis. The molecular defects arising from missense variants were analysed in MDCK-II and AD-293 cells.

RESULTS

Defects in a single allele of ABCB4 were identified in nine subjects. They included one small insertion (p.I1242Nfs), one nonsense mutation (p.R144X) and six missense changes (p.T175A, p.G228R, p.A250T, p.S320F, p.P352L and p.A934T). In four children, these defects in ABCB4 co-existed with various medical conditions. In vitro phenotyping of the six missense variants revealed that four (T175A, G228R, S320F and A934T) led to reduced MDR3 protein levels. Two mutations (G228R and A934T) resulted in trapping of the protein in the endoplasmic reticulum. Phosphatidylcholine efflux activity was decreased to 56-18% of reference levels for MDR3 mutants T175A, A250T and S320F. The G228R, P352L and A934T mutants were found to be non-functional.

CONCLUSIONS

These results illustrate the varying effects of ABCB4 missense mutations and suggest that even a modest reduction in MDR3 activity may contribute or predispose to the onset of cholestatic liver disease in the paediatric age.

Autoimmune BSEP disease: disease recurrence after liver transplantation for progressive familial intrahepatic cholestasis

Severe cholestasis may result in end-stage liver disease with the need of liver transplantation (LTX). In children, about 10 % of LTX are necessary because of cholestatic liver diseases. Apart from bile duct atresia, three types of progressive familial intrahepatic cholestasis (PFIC) are common causes of severe cholestasis in children. The three subtypes of PFIC are defined by the involved genes: PFIC-1, PFIC-2, and PFIC-3 are due to mutations of P-type ATPase ATP8B1 (familial intrahepatic cholestasis 1, FIC1), the ATP binding cassette transporter ABCB11 (bile salt export pump, BSEP), or ABCB4 (multidrug resistance protein 3, MDR3), respectively. All transporters are localized in the canalicular membrane of hepatocytes and together mediate bile salt and phospholipid transport. In some patients with PFIC-2 disease, recurrence has been observed after LTX, which mimics a PFIC phenotype. It could be shown by several groups that inhibitory anti-BSEP antibodies emerge, which most likely cause disease recurrence. The prevalence of severe BSEP mutations (e.g., splice site and premature stop codon mutations) is very high in this group of patients. These mutations often result in the complete absence of BSEP, which likely accounts for an insufficient auto-tolerance against BSEP. Although many aspects of this "new" disease are not fully elucidated, the possibility of anti-BSEP antibody formation has implications for the pre- and posttransplant management of PFIC-2 patients. This review will summarize the current knowledge including diagnosis, pathomechanisms, and management of "autoimmune BSEP disease."

Pathophysiology and Diseases of the Proximal Pathways of the Biliary System

CONTEXT

Diseases of the proximal pathways of the biliary system can be divided into those that affect the interlobular bile ducts and those that affect the bile canaliculi. The former include primary biliary cirrhosis, small-duct variant of primary sclerosing cholangitis, graft-versus-host disease, and drug-induced liver injury, whereas the latter include progressive familial intrahepatic cholestasis, benign recurrent intrahepatic cholestasis, intrahepatic cholestasis of pregnancy, and drug-induced liver injury.

OBJECTIVE

To summarize the current state of knowledge of diseases of the proximal pathways of the biliary system, with special emphasis on clinical presentation, pathological features, and differential diagnosis.

DATA SOURCES

Clinicopathological information was extracted from pertinent published literature.

CONCLUSIONS

Care of the patient with cholestasis hinges on identifying the etiology. Diagnostic steps in cholestatic conditions comprise a thorough patient history, abdominal imaging, distinct serological studies, and liver biopsy. Primary biliary cirrhosis is characterized by distinctive serological and histological findings. The small-duct variant of primary sclerosing cholangitis is very rare and difficult to diagnose; imaging of the bile ducts is not helpful. Graft-versus-host disease is characterized by damage and loss of intrahepatic bile ducts. Drugs can cause injury variably at the level of bile canaliculus or the interlobular bile duct. Loss of bile ducts may be seen with primary biliary cirrhosis, primary sclerosing cholangitis, graft-versus-host disease, and drug-induced liver injury. Progressive familial intrahepatic cholestasis and progressive familial intrahepatic cholestasis represent 2 extreme ends of the spectrum of abnormalities in transporters responsible for bile formation. Intrahepatic cholestasis of pregnancy has a variable incidence in different parts of the world and may be due to abnormalities in transporter molecules.

Byler disease: early natural history

OBJECTIVES

Byler disease, originally described in Amish kindred, results from mutations in ATPase Class I Type 8b Member 1 (ATP8b1). Specific clinical reports of Amish Byler disease were last published 40 years ago. These investigations were directed at the present detailed clinical understanding of the early course of hepatic manifestations of Byler disease.

METHODS

This study analyzed routine clinical practice and outcomes of children with Byler disease (defined by homozygous c.923G>T mutation in ATP8b1), who initially presented to Children's Hospital of Pittsburgh of UPMC between January 2007 and October 2014. Data were analyzed to the earlier of 24 months of age or partial external biliary diversion.

RESULTS

Six children presented between 1 and 135 days of life: 2 presented with newborn direct hyperbilirubinemia, 2 had complications of coagulopathy, 1 had failure to thrive and rickets, and 1 sibling was identified by newborn genetic testing. Intensive fat-soluble vitamin supplementation was required to prevent insufficiencies in vitamins D, E, and K. Hyperbilirubinemia was variable both over time and between children. Serum bile acid levels were elevated, whereas γ-glutamyltranspeptidase levels were low normal. Scratching behavior (pruritus) was intractable in 4 of 6 children with onset between 6 and 12 months of age. Features of portal hypertension were not observed. Partial external biliary diversion was used during the second year of life in 4 children.

CONCLUSIONS

Detailed analysis of Byler disease revealed varied disease presentation and course. Nutritional issues and pruritus dominated the clinical picture in the first 2 years of life.

A novel ABCB11 mutation in an Iranian girl with progressive familial intrahepatic cholestasis

Progressive familial intrahepatic cholestasis is an autosomal recessive liver disorder caused by (biallelic) mutations in the ATP8B1 of ABCB11 gene. A nine-year-old girl with cholestasis was referred for genetic counseling. She had a family history of cholestasis in two previous expired siblings. Genetic analysis of the ABCB11 gene led to the identification of a novel homozygous mutation in exon 25. The mutation 3593- A > G lead to a missense mutation at the amino acid level (His1198Arg). This mutation caused PFIC2 due to abnormal function in the bile salt export pump protein (BSEP).

Bile salt export pump deficiency: A de novo mutation in a child compound heterozygous for ABCB11. Laboratory investigation to study pathogenic role and transmission of two novel ABCB11 mutations

Progressive familial intrahepatic cholestasis (PFIC) is a heterogeneous group of autosomal disorders. PFIC type 2 is due to mutation in ABCB11, the gene encoding the bile salt export pump (BSEP) protein. The aim of the study was to describe a child with a de novo mutation in a compound heterozygous for ABCB11 gene. We report a 1.7-year-old girl who presented with pruritus, jaundice and liver dysfunction of PFIC type 2. Immunohistochemistry and molecular analysis are described. Liver biopsy showed micronodular cirrhosis and immunohistochemical staining for BSEP, the protein encoded by ABCB11, displayed a patchy and faint reactivity. Molecular analysis revealed two novel mutations of ABCB11. We give details that one mutation is transmitted by the mother while the second one appears a de novo mutation as mutations or a potential mosaicism were ruled out in the natural father. We further speculate that the ABCB11 mutations do not prevent BSEP glycoprotein to be expressed at the canalicular pole of hepatocytes, but interfere with its ability to export bile salts. As in most instances, mutational analysis is performed following the histochemical demonstration of an undetectable BSEP on liver biopsy specimen. This case stresses that clinical PFIC with an attenuated rather than absent BSEP immunostaining can still be due to ABCB11 mutations presumably encoding a functionally deficient protein.

Phospholipase D2 mediates signaling by ATPase class I type 8B membrane 1

Functional defects in ATPase class I type 8B membrane 1 (ATP8B1 or familial intrahepatic cholestasis 1, FIC1) lead to cholestasis by mechanism(s) that are not fully understood. One proposed pathophysiology involves aberrant signaling to the bile acid sensor, the farnesoid X receptor (FXR), via protein kinase C ζ (PKCζ). The following cell line-based studies investigated whether phospholipase D2 may transduce a signal from FIC1 to FXR. PLD2 gain of function led to activation of the bile salt export pump (BSEP) promoter, a well-characterized FXR response. BSEP activation by PLD2 could be blocked by abrogating either PKCζ or FXR signaling. PLD2 loss of function led to a reduction in BSEP promoter activity. In addition, a variety of proteins that are activated by FXR, including BSEP, were reduced in HepG2 cells treated with PLD2 siRNA. Similar effects were observed in freshly isolated human hepatocytes. Activation of BSEP by FIC1 gain of function was blocked when PLD2 but not PLD1 was silenced. Overexpression of wild-type but not Byler mutant FIC1 led to an increase in membrane associated PLD activity. An intermediate level of activation of PLD activity was induced when a benign recurrent intrahepatic cholestasis FIC1 mutant construct was expressed. These studies show that FIC1 signals to FXR via a signaling pathway including PLD2 and PKCζ.

The bile salt export pump (BSEP) in health and disease

The bile salt export pump (BSEP) is the major transporter for the secretion of bile acids from hepatocytes into bile in humans. Mutations of BSEP are associated with cholestatic liver diseases of varying severity including progressive familial intrahepatic cholestasis type 2 (PFIC-2), benign recurrent intrahepatic cholestasis type 2 (BRIC-2) and genetic polymorphisms are linked to intrahepatic cholestasis of pregnancy (ICP) and drug-induced liver injury (DILI). Detailed analysis of these diseases has considerably increased our knowledge about physiology and pathophysiology of bile secretion in humans. This review focuses on expression, localization, and function, short- and long-term regulation of BSEP as well as diseases association and treatment options for BSEP-associated diseases.

Chinese children with chronic intrahepatic cholestasis and high γ-glutamyl transpeptidase: clinical features and association with ABCB4 mutations

OBJECTIVE

The aims of the present study was to study the significance of ABCB4 mutations in mainland Chinese children with chronic intrahepatic cholestasis and to correlate genetic findings with clinical features and response to ursodeoxycholic acid (UDCA) therapy.

METHODS

Thirteen patients with chronic intrahepatic cholestasis and elevated serum γ-glutamyl transpeptidase activity of unknown cause were enrolled in a single pediatric center. All of the encoding exons and flanking areas of ABCB4 were sequenced. Available liver biopsy specimens were immunostained for multidrug resistance protein 3. The clinical features, biochemical parameters, and responses to therapy were compared with patients with or without ABCB4 mutation(s).

RESULTS

Six different ABCB4 mutations were identified in 3 patients; each patient was a compound heterozygote. Apart from c.139C>T (p.R47X), all were novel, including c.344+2_+3insT, c.1376A>G (p.D459G), c.1745G>A (p.R582Q), c.2077_2078delC (p.P693HfsX698), and c.3825_3826delA (p.M1276WfsX1308). Absent or reduced multidrug resistance protein 3 canalicular immunostaining was demonstrated in patients with ABCB4 mutations. Serum total bile acid levels were higher in patients with ABCB4 mutations than in patients without ABCB4 mutations (352.5 ± 97.0 vs 55.9 ± 50.4 μmol/L, P = 7.32E-05). There was no difference in other biochemical parameters between patients with and without ABCB4 mutations. After oral UDCA administration in 3 patients with ABCB4 mutations, pruritus disappeared, growth improved, spleen size decreased, and platelet counts increased. In the 10 patients without ABCB4 mutations, an inconsistent response to UDCA therapy was observed.

CONCLUSIONS

In mainland Chinese children, some cases of chronic intrahepatic cholestasis with high γ-glutamyl transpeptidase could be attributed to ABCB4 mutations. UDCA administration partially improved clinical symptoms and liver function.

Liver biopsy in modern clinical practice: a pediatric point-of-view

Liver biopsy remains the foundation of evaluation and management of liver disease in children, although the role of the liver biopsy is changing with development of alternative methods of diagnosis and advancement of hepatic imaging techniques. The indications for liver biopsy are evolving as current knowledge of etiologies, noninvasive biomarker alternatives, and treatment options in pediatric liver disease are expanding. The procedure can often be complicated in children by technical difficulties, cost, and smaller specimen size. Communication and partnership of clinicians with pathologists experienced in pediatric liver diseases are essential. DNA sequencing, novel imaging modalities, noninvasive biomarkers of fibrosis and apoptosis, proteomics, and genome-wide association studies offer potential alternative methods for evaluation of liver disease in children. This review presents specific indications, considerations, methods, complications, contraindications, and alternatives for pediatric liver biopsy.

Use of hepatotoxic drugs in chronic liver disease

Cirrhosis and chronic liver disease are common illnesses that cause high mortality and require treatment. Medication use in these patients may be challenging because of idiosyncratic or dose-dependent drug toxicity. Therefore, drug choice and drug dose adaptations play an important role. The objective of this clinical review is to discuss the literature about and challenges in drug use in patients with chronic liver disease. To make good decisions regarding drug choice and dose adjustments in these patients, well-defined clinical information about diagnoses and laboratory results (creatinine, international normalized ratio, bilirubin, and serologies) as well as in some instances, pathological findings like liver biopsies are needed. In a second step, these data should be organized in electronically supported clinical decision systems, which can then assist providers in making choices about medication selection and dosage. In summary, although substantial research has been done in the field of drug use in patients with liver dysfunction, a great deal also remains to be learned. Although many of these patients can now be identified, it is still very difficult to assess their individual level of hepatic function. The degree of risk associated with drug use and how best to use medications in these patients represents an important area for further study. In the future, pharmacogenomics and electronic linking of clinical data may well prove helpful for making decisions about optimal drug choices in this complex group of patients.

Normalization of serum bile acids after partial external biliary diversion indicates an excellent long-term outcome in children with progressive familial intrahepatic cholestasis

BACKGROUND/PURPOSE

The surgical treatment for patients with progressive familial intrahepatic cholestasis (PFIC) is either liver transplantation (LTX) or partial external biliary diversion (PEBD). Both procedures achieve a good short-term outcome. However, the treatment strategy for these children remains controversial because the long-term outcome after PEBD is unknown. The aim of our study was to assess the long-term outcome and complications after PEBD in our institution.

METHODS

We retrospectively analyzed the characteristics of all patients with PFIC undergoing PEBD in our department from 1994 to 2008. The course of serum bile acids, pruritus, and liver enzymes was assessed in a regular follow-up.

RESULTS

Twenty-four patients underwent PEBD. Thirteen patients (54%) improved significantly, with a normalization of serum bile acids (P < .001 vs postoperatively) and lessened pruritus (P < .05 vs preoperatively) at 12 months after PEBD. None of these patients showed progression of cholestasis during a median follow-up of 9.8 years (range, 1.6-14.3 years). Partial external biliary diversion failed to normalize bile acids in 11 patients, of whom 9 required secondary LTX at a 1-year follow-up, with a median interval of 1.9 years (range, 0.5-3.8 years). All 7 patients (100%) with liver cirrhosis at the time of PEBD and 2 of 17 patients without cirrhosis (12%) required secondary LTX (P < .001).

CONCLUSIONS

Clinical improvement with normalization of serum bile acids within 1 year was associated with an excellent long-term outcome in patients with PEBD. The presence of liver cirrhosis at the time of PEBD indicated an unfavorable outcome. Thus, we recommend primary LTX only in PFIC patients with liver cirrhosis.

Description of two new ABCB11 mutations responsible for type 2 benign recurrent intrahepatic cholestasis in a French-Canadian family

Benign recurrent intrahepatic cholestasis is a rare clinical entity that is caused by mutations in the canalicular transport genes. The present report describes two individuals from the same family whose symptoms were typical of the clinical characteristics of type 2 benign recurrent intrahepatic cholestasis. Sequencing of the ABCB11 gene revealed two previously unreported mutations that predict the absence of expression of the protein. The clinical presentation of the current cases are discussed, as are the differential diagnosis and genetic characteristics of the hereditary cholestatic disorders, overemphasizing the possibility of making a definite genetic diagnosis.

Morphologic findings in progressive familial intrahepatic cholestasis 2 (PFIC2): correlation with genetic and immunohistochemical studies

Progressive familial intrahepatic cholestasis, type 2 (PFIC2), characterized by cholestasis in infancy that may progress to cirrhosis, is caused by mutation in ABCB11, which encodes bile salt export pump (BSEP). We correlated histopathologic, immunohistochemical, and ultrastructural features in PFIC2 with specific mutations and clinical course. Twelve patients with clinical PFIC2 and ABCB11 mutations were identified, and 22 liver biopsy and explant specimens were assessed. All had hepatocellular cholestasis; most had canalicular bile plugs. At least 1 specimen from every patient had centrizonal/sinusoidal fibrosis, often with periportal fibrosis. Neonatal hepatitis-like features (inflammation, giant cells, necrosis) varied. In 2 of the 5 patients with paired specimens obtained >6 months apart, lobular and portal fibrosis worsened. Transmission electron microscopy (EM) in all 9 patients studied showed canalicular dilatation, microvilli loss, abnormal mitochondrial internal structure, and varying intracanalicular accumulation of finely granular bile. Canalicular staining for BSEP was absent in 10 patients and present in 2 patients, 1 of whom had intermittent symptoms. ABCB11 sequencing of all patients identified 6 novel and 10 previously described mutations, with nonsense, missense, and/or noncoding mutations in the 10 patients without immunohistochemically demonstrable BSEP. Missense and/or noncoding mutations were identified in the 2 patients with demonstrable BSEP, whose clinical course was more indolent. Mutations ending ABCB11 transcription appear linked, through hepatocellular necrosis and fibrosis, to worse outcome. In conclusion, light microscopy and electron microscopy findings in clinical PFIC2 can support diagnosis, but are variable and nonspecific. Therefore, no correlation between specific mutations and histopathology is yet possible.

Button cholecystostomy for management of progressive familial intrahepatic cholestasis syndromes

BACKGROUND/PURPOSE

Progressive familial intrahepatic cholestasis syndromes are characterized by impaired bile acid secretion resulting in pruritus, coagulopathy, diarrhea, and malnutrition leading to progressive liver failure and death in childhood. Partial internal or external biliary drainage can relieve symptoms and slow the progression of the disease. Objections to partial external biliary drainage include the need for a permanent biliary stoma with all the inherent complications of a stoma. We propose a novel approach to these diseases--placement of a "button" cholecystostomy tube.

METHODS

Under general anesthesia and through a small right subcostal incision, a MIC-KEY button (Kimberly-Clark Worldwide, Inc, Draper, UT) is inserted into the mobilized fundus of the gallbladder and secured with 2 purse-string sutures. Time of drainage is adjusted to relieve pruritus.

RESULTS

Three children with progressive familial intrahepatic cholestasis achieved adequate bile drainage via the cholecystostomy button to relieve pruritus for 1, 2, and 2 ½ years postoperatively, with drainage periods of 12 to 14 hours per day. There were no episodes of cholangitis. Dislodged tubes can be replaced, or stones can be retrieved via the tract that is formed. Patient (parent) acceptance has been excellent.

CONCLUSION

Button cholecystostomy is simple to perform, relieves pruritus with intermittent (nighttime) drainage, avoids complications of a permanent stoma, avoids an enteric anastomosis, and is accepted by parents.

The role of the sodium-taurocholate cotransporting polypeptide (NTCP) and of the bile salt export pump (BSEP) in physiology and pathophysiology of bile formation

Bile formation is an important function of the liver. Bile salts are a major constituent of bile and are secreted by hepatocytes into bile and delivered into the small intestine, where they assist in fat digestion. In the small intestine, bile salts are almost quantitatively reclaimed and transported back via the portal circulation to the liver. In the liver, hepatocytes take up bile salts and secrete them again into bile for ongoing enterohepatic circulation. Uptake of bile salts into hepatocytes occurs largely in a sodium-dependent manner by the sodium taurocholate cotransporting polypeptide NTCP. The transport properties of NTCP have been extensively characterized. It is an electrogenic member of the solute carrier family of transporters (SLC10A1) and transports predominantly bile salts and sulfated compounds, but is also able to mediate transport of additional substrates, such as thyroid hormones, drugs and toxins. It is highly regulated under physiologic and pathophysiologic conditions. Regulation of NTCP copes with changes of bile salt load to hepatocytes and prevents entry of cytotoxic bile salts during liver disease. Canalicular export of bile salts is mediated by the ATP-binding cassette transporter bile salt export pump BSEP (ABCB11). BSEP constitutes the rate limiting step of hepatocellular bile salt transport and drives enterohepatic circulation of bile salts. It is extensively regulated to keep intracellular bile salt levels low under normal and pathophysiologic situations. Mutations in the BSEP gene lead to severe progressive familial intrahepatic cholestasis. The substrates of BSEP are practically restricted to bile salts and their metabolites. It is, however, subject to inhibition by endogenous metabolites or by drugs. A sustained inhibition will lead to acquired cholestasis, which can end in liver injury.

Clinical features and genotype-phenotype correlations in children with progressive familial intrahepatic cholestasis type 3 related to ABCB4 mutations

OBJECTIVES

The aim of the study was to estimate the frequency of ABCB4 mutations among children with chronic intrahepatic cholestasis with elevated gamma-glutamyl-transpeptidase (γ-GT) activity and to characterize the genotypes with respect to severity of symptoms, response to ursodeoxycholic acid therapy, and outcome.

PATIENTS AND METHODS

Molecular analysis of ABCB4 in 133 Italian children was performed, and ABCB4 mutations were classified as disease-causing mutations or benign substitutions according to the prediction algorithm PolyPhen.

RESULTS

: Twenty-eight patients were identified carrying 31 mutations (20 disease causing). Twenty patients carried 2 mutated alleles and 8 only 1. At presentation (1-204 months), 20 children were symptomatic with jaundice and/or pruritus, whereas in 8 biochemical cholestasis was a fortuitous finding. Cirrhosis developed in 15 and 6 progressed to terminal liver failure. Disease-causing mutations on both alleles were found to be associated with reduced liver expression of ABCB4 protein, lack of response to ursodeoxycholic acid therapy, and progression to cirrhosis and end-stage liver disease, whereas mild genotypes, including single heterozygous mutations, were generally associated with less severe disease and, often, absence of symptoms.

CONCLUSIONS

ABCB4 mutations are responsible for a chronic liver disease in more than one-third of patients with chronic intrahepatic cholestasis and elevated γ-GT activity. In patients with severe ABCB4 genotype, the disease is often progressive with risk of developing cirrhosis and liver failure during the first 2 decades of life. Patients with mild genotypes, including single heterozygous mutations, have variable expressions of liver disease that may be influenced by comorbidity factors and modulated by still unknown genetic modifiers.

Interference with bile salt export pump function is a susceptibility factor for human liver injury in drug development

The bile salt export pump (BSEP) is an efflux transporter, driving the elimination of endobiotic and xenobiotic substrates from hepatocytes into the bile. More specifically, it is responsible for the elimination of monovalent, conjugated bile salts, with little or no assistance from other apical transporters. Disruption of BSEP activity through genetic disorders is known to manifest in clinical liver injury such as progressive familial intrahepatic cholestasis type 2. Drug-induced disruption of BSEP is hypothesized to play a role in the development of liver injury for several marketed or withdrawn therapeutics. Unfortunately, preclinical animal models have been poor predictors of the liver injury associated with BSEP interference observed for humans, possibly because of interspecies differences in bile acid composition, differences in hepatobiliary transporter modulation or constitutive expression, as well as other mechanisms. Thus, a BSEP-mediated liver liability may go undetected until the later stages of drug development, such as during clinical trials or even postlicensing. In the absence of a relevant preclinical test system for BSEP-mediated liver injury, the toxicological relevance of available in vitro models to human health rely on the use of benchmark compounds with known clinical outcomes, such as marketed or withdrawn drugs. In this study, membrane vesicles harvested from BSEP-transfected insect cells were used to assess the activity of more than 200 benchmark compounds to thoroughly investigate the relationship between interference with BSEP function and liver injury. The data suggest a relatively strong association between the pharmacological interference with BSEP function and human hepatotoxicity. Although the most accurate translation of risk would incorporate pharmacological potency, pharmacokinetics, clearance mechanisms, tissue distribution, physicochemical properties, indication, and other drug attributes, the additional understanding of a compound's potency for BSEP interference should help to limit or avoid BSEP-related liver liabilities in humans that are not often detected by standard preclinical animal models.

Recurrent low gamma-glutamyl transpeptidase cholestasis following liver transplantation for bile salt export pump (BSEP) disease (posttransplant recurrent BSEP disease)

Bile salt export pump (BSEP) deficiency is a hereditary cholestatic syndrome that results from mutations in the ABCB11 (ATP-binding cassette B11) gene. Severely affected patients develop end-stage liver disease in the first decade of life. Liver transplantation has traditionally been thought of as curative for BSEP disease. We describe the clinical course of 6 patients who developed recurrent low gamma-glutamyl transpeptidase cholestasis, that mimicks BSEP disease, following transplantation. All had documented genetic defects in ABCB11 that were predicted to lead to a congenital absence of BSEP protein. The time to development of recurrence was variable; 4 underwent repeat liver transplantation for complications of recurrent disease and all 4 again developed recurrent disease after retransplantation. Siblings of these patients who also underwent liver transplantation for BSEP disease have not developed "recurrent" disease. Three of the patients with "recurrent" disease ultimately died, 2 as a direct result of complications of their liver disease.