Bile composition in Alagille Syndrome and PFIC patients having Partial External Biliary Diversion

Event-free survival of maralixibat-treated patients with Alagille syndrome compared to a real-world cohort from GALA

BACKGROUND AND AIMS

Alagille syndrome (ALGS) is characterized by chronic cholestasis with associated pruritus and extrahepatic anomalies. Maralixibat, an ileal bile acid transporter inhibitor, is an approved pharmacologic therapy for cholestatic pruritus in ALGS. Since long-term placebo-controlled studies are not feasible or ethical in children with rare diseases, a novel approach was taken comparing 6-year outcomes from maralixibat trials with an aligned and harmonized natural history cohort from the G lobal AL agille A lliance (GALA) study.

APPROACH AND RESULTS

Maralixibat trials comprise 84 patients with ALGS with up to 6 years of treatment. GALA contains retrospective data from 1438 participants. GALA was filtered to align with key maralixibat eligibility criteria, yielding 469 participants. Serum bile acids could not be included in the GALA filtering criteria as these are not routinely performed in clinical practice. Index time was determined through maximum likelihood estimation in an effort to align the disease severity between the two cohorts with the initiation of maralixibat. Event-free survival, defined as the time to first event of manifestations of portal hypertension (variceal bleeding, ascites requiring therapy), surgical biliary diversion, liver transplant, or death, was analyzed by Cox proportional hazards methods. Sensitivity analyses and adjustments for covariates were applied. Age, total bilirubin, gamma-glutamyl transferase, and alanine aminotransferase were balanced between groups with no statistical differences. Event-free survival in the maralixibat cohort was significantly better than the GALA cohort (HR, 0.305; 95% CI, 0.189-0.491; p <0.0001). Multiple sensitivity and subgroup analyses (including serum bile acid availability) showed similar findings.

CONCLUSIONS

This study demonstrates a novel application of a robust statistical method to evaluate outcomes in long-term intervention studies where placebo comparisons are not feasible, providing wide application for rare diseases. This comparison with real-world natural history data suggests that maralixibat improves event-free survival in patients with ALGS.

Odevixibat: A Novel Bile Salt Inhibitor Treatment for Pruritus in Progressive Familial Intrahepatic Cholestasis

Chronic pruritus is defined as an itch lasting greater than six weeks. It can manifest from a wide variety of etiologies, as many different substances can act as pruritogens, such as steroids, histamine, progesterone, endogenous opioids, and serotonin. In the setting of cholestatic liver disease, increased bile acids play a major role in chronic pruritus. The itching in cholestatic liver disease is worsened in intensity at night and localized frequently to the palms, soles, knees, and other pressure sites. It can be hard to manage, affecting the quality of sleep and causing irritability, poor attention, and, in some cases, depression. One such disease that results from chronic pruritus is progressive familial intrahepatic cholestasis (PFIC), a group of uncommon hereditary disorders that affects the formation of bile and its outflow from the liver. Previously, the drug ursodeoxycholic acid was used to help manage pruritus or surgical procedures, e.g., partial external biliary diversion or partial internal biliary diversion, to help control complications of the disease. This literature review will discuss three clinical studies covering the effectiveness of odevixibat in treating pruritus in patients with PFIC. Odevixibat (Bylvay) is an oral drug that has been FDA-approved to treat pruritus in patients three months of age and older with PFIC. Odevixibat prevents the reabsorption of bile salts in the intestines, resulting in decreased levels of bile salts via their excretion in stool. Several studies have determined that the drug is well tolerated and provides a nonsurgical, pharmacological treatment alternative for those with PFIC.

Biliary diversion in progressive familial intrahepatic cholestasis: a systematic review and meta-analysis

BACKGROUND

Biliary diversion (BD) is indicated in progressive familial intrahepatic cholestasis (PFIC) with refractory pruritus. Three types-partial external biliary drainage (PEBD), partial internal biliary drainage (PIBD), and ileal exclusion (IE) are described, with no consensus about the relative efficacy of these procedures.

METHODS

PubMed, Scopus, and Google Scholar were searched for publications on PFIC and BD. Improvement in pruritus, serum bile acid (BA), and need for liver transplantation (LT) were compared between the various BD procedures.

RESULTS

25 studies [424 children (PEBD-301, PIBD-93, IE-30)] were included. Pruritus resolved in 59.5% [PIBD:72% (95%CI 43-96%), PEBD:57% (95%CI 43-71%) and IE:48% (95%CI 14-82%)] cases. Significant overlap in confidence intervals indicated no significant differences. Absolute decrease in BA (AUROC-0.72) and bilirubin (AUROC-0.69) discriminated responders and non-responders. Eventually, 27% required LT: PIBD 10.7%, PEBD32%, IE 27%. The post-operative BA (AUROC-0.9) and bilirubin (AUROC-0.85) determined need for LT. Complications were commoner in PEBD than PIBD (38% vs 21.8%: p=0.02).

CONCLUSION

59.5% children have pruritus relief after BD and 27% need LT. PIBD has lower complications and LT requirement than PEBD. However, this requires cautious interpretation as the 2 groups differed in PFIC type and follow-up duration.

A Current Understanding of Bile Acids in Chronic Liver Disease

Chronic liver disease (CLD) is one of the leading causes of disability-adjusted life years in many countries. A recent understanding of nuclear bile acid receptor pathways has increased focus on the impact of crosstalk between the gut, bile acids, and liver on liver pathology. While conventionally used in cholestatic disorders and to dissolve gallstones, the discovery of bile acids' influence on the gut microbiome and human metabolism offers a unique potential for their utility in early and advanced liver diseases because of diverse etiologies. Based on these findings, preclinical studies using bile acid-based molecules have shown encouraging results at addressing liver inflammation and fibrosis. Emerging data also suggest that bile acid profiles change distinctively across various causes of liver disease. We summarize the current knowledge and evidence related to bile acids in health and disease and discuss culminated and ongoing therapeutic trials of bile acid derivatives in CLD. In the near future, further evidence in this area might help clinicians better detect and manage liver diseases.

Potential of ileal bile acid transporter inhibition as a therapeutic target in Alagille syndrome and progressive familial intrahepatic cholestasis

Alagille syndrome (ALGS) and progressive familial intrahepatic cholestasis (PFIC) are rare, inherited cholestatic liver disorders that manifest in infants and children and are associated with impaired bile flow (ie cholestasis), pruritus and potentially fatal liver disease. There are no effective or approved pharmacologic treatments for these diseases (standard medical treatments are supportive only), and new, noninvasive options would be valuable. Typically, bile acids undergo biliary secretion and intestinal reabsorption (ie enterohepatic circulation). However, in these diseases, disrupted secretion of bile acids leads to their accumulation in the liver, which is thought to underlie pruritus and liver-damaging inflammation. One approach to reducing pathologic bile acid accumulation in the body is surgical biliary diversion, which interrupts the enterohepatic circulation (eg by diverting bile acids to an external stoma). These procedures can normalize serum bile acids, reduce pruritus and liver injury and improve quality of life. A novel, nonsurgical approach to interrupting the enterohepatic circulation is inhibition of the ileal bile acid transporter (IBAT), a key molecule in the enterohepatic circulation that reabsorbs bile acids from the intestine. IBAT inhibition has been shown to reduce serum bile acids and pruritus in trials of paediatric cholestatic liver diseases. This review explores the rationale of inhibition of the IBAT as a therapeutic target, describes IBAT inhibitors in development and summarizes the current data on interrupting the enterohepatic circulation as treatment for cholestatic liver diseases including ALGS and PFIC.

Surgical diversion of enterohepatic circulation in pediatric cholestasis

Progressive familial intrahepatic cholestasis (PFIC) and Alagille syndrome (AS) are conditions caused by either an autosomal recessive or an autosomal dominant genetic defect, and they are both characterized by cholestasis, jaundice, and severe debilitating pruritus refractory to medical management. Before the advent of liver transplantation, most PFIC patients would die from end-stage liver disease in the first decade of life. Although liver transplantation has led to patients' survival, disease recurrence (PFIC-2) and severe extra-hepatic manifestations of the disease (PFIC-1) occurred post transplant. In the late 1980s, Whitington described the use of partial external biliary diversion in PFIC and AS patients as a successful way to improve symptoms and decrease circulating bile acid serum concentrations. Since then, other diversion techniques have been described (ileal exclusion and partial internal biliary diversion). These techniques have the benefit of avoiding a stoma, but equivalent results have not been demonstrated (recurrence of cholestasis after ileal exclusion, limited follow up after internal biliary diversion). Overall, studies have showed that biliary diversions in children with cholestasis are safe procedures with low morbidity and mortality, and that they can reduce inflammation and ongoing liver injury, therefore delaying or avoiding the need for liver transplantation in some patients.

Systematic Review and Meta-analysis: Partial External Biliary Diversion in Progressive Familial Intrahepatic Cholestasis

OBJECTIVES

We assessed available data on impact of partial external biliary diversion (PEBD) surgery on clinical outcomes in patients with progressive familial intrahepatic cholestasis (PFIC).

METHODS

We performed a systematic literature review (PubMed) and meta-analysis to evaluate relationships between liver biochemistry parameters (serum bile acids, bilirubin, and alanine aminotransferase [ALT]) and early response (pruritus improvement) or long-term outcomes (need for liver transplant) in patients with PFIC who underwent PEBD.

RESULTS

Searches identified 175 publications before September 2018; 16 met inclusion criteria. Receiver operating characteristic (ROC) analysis examined ability of liver biochemistry parameters to discriminate patients who demonstrated early and long-term response to PEBD from those who did not. Regarding pruritus improvement in 155 included patients in aggregate, 104 (67%) were responders, 14 (9%) had partial response, and 37 (24%) were nonresponders. In ROC analyses of individual patient data, post-PEBD serum concentration of bile acids, in particular, could discriminate responders from nonresponders for pruritus improvement (area under the curve, 0.99; P < 0.0001; n = 42); to a lesser extent, this was also true for bilirubin (0.87; P = 0.003; n = 31), whereas ALT could not discriminate responders from nonresponders for pruritus improvement (0.74; P = 0.06; n = 28). Reductions from pre-PEBD values in serum bile acid concentration (0.89; P = 0.0003; n = 32) and bilirubin (0.98; P = 0.002; n = 18) but not ALT (0.62; P = 0.46; n = 18) significantly discriminated decreased aggregate need for liver transplant.

CONCLUSION

Changes in bile acids seem particularly useful in discriminating early and long-term post-PEBD outcomes and may be potential biomarkers of response to interruption of enterohepatic circulation in patients with PFIC.

Genotype correlates with the natural history of severe bile salt export pump deficiency

BACKGROUND & AIMS

Mutations in ABCB11 can cause deficiency of the bile salt export pump (BSEP), leading to cholestasis and end-stage liver disease. Owing to the rarity of the disease, the associations between genotype and natural history, or outcomes following surgical biliary diversion (SBD), remain elusive. We aimed to determine these associations by assembling the largest genetically defined cohort of patients with severe BSEP deficiency to date.

METHODS

This multicentre, retrospective cohort study included 264 patients with homozygous or compound heterozygous pathological ABCB11 mutations. Patients were categorized according to genotypic severity (BSEP1, BSEP2, BSEP3). The predicted residual BSEP transport function decreased with each category.

RESULTS

Genotype severity was strongly associated with native liver survival (NLS, BSEP1 median 20.4 years; BSEP2, 7.0 years; BSEP3, 3.5 years; p <0.001). At 15 years of age, the proportion of patients with hepatocellular carcinoma was 4% in BSEP1, 7% in BSEP2 and 34% in BSEP3 (p = 0.001). SBD was associated with significantly increased NLS (hazard ratio 0.50; 95% CI 0.27-0.94: p = 0.03) in BSEP1 and BSEP2. A serum bile acid concentration below 102 μmol/L or a decrease of at least 75%, each shortly after SBD, reliably predicted NLS of ≥15 years following SBD (each p <0.001).

CONCLUSIONS

The genotype of severe BSEP deficiency strongly predicts long-term NLS, the risk of developing hepatocellular carcinoma, and the chance that SBD will increase NLS. Serum bile acid parameters shortly after SBD can predict long-term NLS.

LAY SUMMARY

This study presents data from the largest genetically defined cohort of patients with severe bile salt export pump deficiency to date. The genotype of patients with severe bile salt export pump deficiency is associated with clinical outcomes and the success of therapeutic interventions. Therefore, genotypic data should be used to guide personalized clinical care throughout childhood and adulthood in patients with this disease.

Jaundice revisited: recent advances in the diagnosis and treatment of inherited cholestatic liver diseases

Background

Jaundice is a common symptom of inherited or acquired liver diseases or a manifestation of diseases involving red blood cell metabolism. Recent progress has elucidated the molecular mechanisms of bile metabolism, hepatocellular transport, bile ductular development, intestinal bile salt reabsorption, and the regulation of bile acids homeostasis.

Main body

The major genetic diseases causing jaundice involve disturbances of bile flow. The insufficiency of bile salts in the intestines leads to fat malabsorption and fat-soluble vitamin deficiencies. Accumulation of excessive bile acids and aberrant metabolites results in hepatocellular injury and biliary cirrhosis. Progressive familial intrahepatic cholestasis (PFIC) is the prototype of genetic liver diseases manifesting jaundice in early childhood, progressive liver fibrosis/cirrhosis, and failure to thrive. The first three types of PFICs identified (PFIC1, PFIC2, and PFIC3) represent defects in FIC1 (ATP8B1), BSEP (ABCB11), or MDR3 (ABCB4). In the last 5 years, new genetic disorders, such as TJP2, FXR, and MYO5B defects, have been demonstrated to cause a similar PFIC phenotype. Inborn errors of bile acid metabolism also cause progressive cholestatic liver injuries. Prompt differential diagnosis is important because oral primary bile acid replacement may effectively reverse liver failure and restore liver functions. DCDC2 is a newly identified genetic disorder causing neonatal sclerosing cholangitis. Other cholestatic genetic disorders may have extra-hepatic manifestations, such as developmental disorders causing ductal plate malformation (Alagille syndrome, polycystic liver/kidney diseases), mitochondrial hepatopathy, and endocrine or chromosomal disorders. The diagnosis of genetic liver diseases has evolved from direct sequencing of a single gene to panel-based next generation sequencing. Whole exome sequencing and whole genome sequencing have been actively investigated in research and clinical studies. Current treatment modalities include medical treatment (ursodeoxycholic acid, cholic acid or chenodeoxycholic acid), surgery (partial biliary diversion and liver transplantation), symptomatic treatment for pruritus, and nutritional therapy. New drug development based on gene-specific treatments, such as apical sodium-dependent bile acid transporter (ASBT) inhibitor, for BSEP defects are underway.

Short conclusion

Understanding the complex pathways of jaundice and cholestasis not only enhance insights into liver pathophysiology but also elucidate many causes of genetic liver diseases and promote the development of novel treatments.

Analysis of surgical interruption of the enterohepatic circulation as a treatment for pediatric cholestasis

To evaluate the efficacy of nontransplant surgery for pediatric cholestasis, 58 clinically diagnosed children, including 20 with Alagille syndrome (ALGS), 16 with familial intrahepatic cholestasis-1 (FIC1), 18 with bile salt export pump (BSEP) disease, and 4 others with low γ-glutamyl transpeptidase disease (levels <100 U/L), were identified across 14 Childhood Liver Disease Research Network (ChiLDReN) centers. Data were collected retrospectively from individuals who collectively had 39 partial external biliary diversions (PEBDs), 11 ileal exclusions (IEs), and seven gallbladder-to-colon (GBC) diversions. Serum total bilirubin decreased after PEBD in FIC1 (8.1 ± 4.0 vs. 2.9 ± 4.1 mg/dL, preoperatively vs. 12-24 months postoperatively, respectively; P = 0.02), but not in ALGS or BSEP. Total serum cholesterol decreased after PEBD in ALGS patients (695 ± 465 vs. 457 ± 319 mg/dL, preoperatively vs. 12-24 months postoperatively, respectively; P = 0.0001). Alanine aminotransferase levels increased in ALGS after PEBD (182 ± 70 vs. 260 ± 73 IU/L, preoperatively vs. 24 months; P = 0.03), but not in FIC1 or BSEP. ALGS, FIC1, and BSEP patients experienced less severely scored pruritus after PEBD (ALGS, 100% vs. 9% severe; FIC1, 64% vs. 10%; BSEP, 50% vs. 20%, preoperatively vs. >24 months postoperatively, respectively; P < 0.001). ALGS patients experienced a trend toward greater freedom from xanthomata after PEBD. There was a trend toward decreased pruritus in FIC1 after IE and GBC. Vitamin K supplementation increased in ALGS after PEBD (33% vs. 77%; P = 0.03). Overall, there were 15 major complications after surgery. Twelve patients (3 ALGS, 3 FIC1, and 6 BSEP) subsequently underwent liver transplantation.

CONCLUSION

This was a multicenter analysis of nontransplant surgical approaches to intrahepatic cholestasis. Approaches vary, are well tolerated, and generally, although not uniformly, result in improvement of pruritus and cholestasis. (Hepatology 2017;65:1645-1654).

Outcomes following partial external biliary diversion in patients with progressive familial intrahepatic cholestasis

BACKGROUND/PURPOSE

PFIC is a family of bile acid (BA) transport disorders that may result in serious liver disease requiring transplantation. We reviewed our experience with PEBD as a method to improve liver function and avoid transplantation.

METHODS

All patients with PFIC were reviewed. Outcomes included changes in serum BA, conversion to ileal bypass (IB), and survival without transplantation. Statistics were obtained using paired t-test and Wilcoxon test.

RESULTS

Thirty-five patients with PFIC were identified. Data were available in 24. Twenty-four children (12 males) underwent PEBD: 10 PFIC-1, 13 PFIC-2, and one PFIC-3. BA levels decreased in PFIC-1 patients (1724±3215 to 11±6μmol/L, P=0.03) and in the single PFIC-3 patient (821 to 11.2μmol/L), but not significantly in PFIC-2 patients (193±99 to 141±118μmol/L, P=0.15). Seven patients were converted to IB. There were no significant changes in BA levels following conversion. Five-year transplant-free survival was 100% in PFIC-1 and PFIC-3, but only 38% (5/13) in PFIC-2 (P=0.004).

CONCLUSION

PEBD is an effective procedure to reduce total BA levels and improve symptoms in PFIC patients. However, it appears to be less efficacious in the PFIC-2 group. The higher BA levels could contribute to ongoing liver damage, and thus a higher transplant rate in PFIC-2 patients.

LEVEL OF EVIDENCE

Level IV.

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."

Liver biopsy in children: position paper of the ESPGHAN Hepatology Committee

Liver biopsy (LB) is still the criterion standard procedure for obtaining liver tissue for histopathological examination and a valuable tool in the diagnosis, prognosis, and management of many parenchymal liver diseases. The aim of this position paper is to summarise the present practice of paediatric LB and make recommendations about its performance. Although histological evaluation of the liver is important in assessing prognosis and exploring treatment, noninvasive techniques (ie, imaging, laboratory markers) may replace use of liver histology. The indications for LB are changing as present knowledge of aetiologies, pathomechanism, and therapeutic options in paediatric liver disease is evolving. Adult and paediatric literature was reviewed to assess the existing clinical practice of LB with focus on the technique, indications, risk of complications, and contraindications in paediatrics. This position paper presents types of LB, indications, complications, contraindications, and an essential checklist for paediatric LB.

MYO5B and bile salt export pump contribute to cholestatic liver disorder in microvillous inclusion disease

Microvillous inclusion disease (MVID) is a congenital disorder of the enterocyte related to mutations in the MYO5B gene, leading to intractable diarrhea often necessitating intestinal transplantation (ITx). Among our cohort of 28 MVID patients, 8 developed a cholestatic liver disease akin to progressive familial intrahepatic cholestasis (PFIC). Our aim was to investigate the mechanisms by which MYO5B mutations affect hepatic biliary function and lead to cholestasis in MVID patients. Clinical and biological features and outcome were reviewed. Pretransplant liver biopsies were analyzed by immunostaining and electron microscopy. Cholestasis occurred before (n = 5) or after (n = 3) ITx and was characterized by intermittent jaundice, intractable pruritus, increased serum bile acid (BA) levels, and normal gamma-glutamyl transpeptidase activity. Liver histology showed canalicular cholestasis, mild-to-moderate fibrosis, and ultrastructural abnormalities of bile canaliculi. Portal fibrosis progressed in 5 patients. No mutation in ABCB11/BSEP or ATP8B1/FIC1 genes were identified. Immunohistochemical studies demonstrated abnormal cytoplasmic distribution of MYO5B, RAB11A, and BSEP in hepatocytes. Interruption of enterohepatic BA cycling after partial external biliary diversion or graft removal proved the most effective to ensure long-term remission.

CONCLUSION

MVID patients are at risk of developing a PFIC-like liver disease that may hamper outcome after ITx. Our results suggest that cholestasis in MVID patients results from (1) impairment of the MYO5B/RAB11A apical recycling endosome pathway in hepatocytes, (2) altered targeting of BSEP to the canalicular membrane, and (3) increased ileal BA absorption. Because cholestasis worsens after ITx, indication of a combined liver ITx should be discussed in MVID patients with severe cholestasis. Future studies will need to address more specifically the effect of MYO5B dysfunction in BA homeostasis.

Combined deletion of Fxr and Shp in mice induces Cyp17a1 and results in juvenile onset cholestasis

Bile acid homeostasis is tightly regulated via a feedback loop operated by the nuclear receptors farnesoid X receptor (FXR) and small heterodimer partner (SHP). Contrary to current models, which place FXR upstream of SHP in a linear regulatory pathway, here we show that the phenotypic consequences in mice of the combined loss of both receptors are much more severe than the relatively modest impact of the loss of either Fxr or Shp alone. Fxr-/-Shp-/- mice exhibited cholestasis and liver injury as early as 3 weeks of age, and this was linked to the dysregulation of bile acid homeostatic genes, particularly cytochrome P450, family 7, subfamily a, polypeptide 1 (Cyp7a1). In addition, double-knockout mice showed misregulation of genes in the C21 steroid biosynthesis pathway, with strong induction of cytochrome P450, family 17, subfamily a, polypeptide 1 (Cyp17a1), resulting in elevated serum levels of its enzymatic product 17-hydroxyprogesterone (17-OHP). Treatment of WT mice with 17-OHP was sufficient to induce liver injury that reproduced many of the histopathological features observed in the double-knockout mice. Therefore, our data indicate a pathologic role for increased production of 17-hydroxy steroid metabolites in liver injury and suggest that Fxr-/-Shp-/- mice could provide a model for juvenile onset cholestasis.

ATP8B1 and ABCB11 analysis in 62 children with normal gamma-glutamyl transferase progressive familial intrahepatic cholestasis (PFIC): phenotypic differences between PFIC1 and PFIC2 and natural history

Progressive familial intrahepatic cholestasis (PFIC) types 1 and 2 are characterized by normal serum gamma-glutamyl transferase (GGT) activity and are due to mutations in ATP8B1 (encoding FIC1) and ABCB11 (encoding bile salt export pump [BSEP]), respectively. Our goal was to evaluate the features that may distinguish PFIC1 from PFIC2 and ease their diagnosis. We retrospectively reviewed charts of 62 children with normal-GGT PFIC in whom a search for ATP8B1 and/or ABCB11 mutation, liver BSEP immunostaining, and/or bile analysis were performed. Based on genetic testing, 13 patients were PFIC1 and 39 PFIC2. The PFIC origin remained unknown in 10 cases. PFIC2 patients had a higher tendency to develop neonatal cholestasis. High serum alanine aminotransferase and alphafetoprotein levels, severe lobular lesions with giant hepatocytes, early liver failure, cholelithiasis, hepatocellular carcinoma, very low biliary bile acid concentration, and negative BSEP canalicular staining suggest PFIC2, whereas an absence of these signs and/or presence of extrahepatic manifestations suggest PFIC1. The PFIC1 and PFIC2 phenotypes were not clearly correlated with mutation types, but we found tendencies for a better prognosis and response to ursodeoxycholic acid (UDCA) or biliary diversion (BD) in a few children with missense mutations. Combination of UDCA, BD, and liver transplantation allowed 87% of normal-GGT PFIC patients to be alive at a median age of 10.5 years (1-36), half of them without liver transplantation.

CONCLUSION

PFIC1 and PFIC2 differ clinically, biochemically, and histologically at presentation and/or during the disease course. A small proportion of normal-GGT PFIC is likely not due to ATP8B1 or ABCB11 mutations.

Liver disease associated with canalicular transport defects: current and future therapies

Bile formation at the canalicular membrane is a delicate process. This is illustrated by inherited liver diseases due to mutations in ATP8B1, ABCB11, ABCB4, ABCC2 and ABCG5/8, all encoding hepatocanalicular transporters. Effective treatment of these canalicular transport defects is a clinical and scientific challenge that is still ongoing. Current evidence indicates that ursodeoxycholic acid (UDCA) can be effective in selected patients with PFIC3 (ABCB4 deficiency), while rifampicin reduces pruritus in patients with PFIC1 (ATP8B1 deficiency) and PFIC2 (ABCB11 deficiency), and might abort cholestatic episodes in BRIC (mild ATP8B1 or ABCB11 deficiency). Cholestyramine is essential in the treatment of sitosterolemia (ABCG5/8 deficiency). Most patients with PFIC1 and PFIC2 will benefit from partial biliary drainage. Nevertheless liver transplantation is needed in a substantial proportion of these patients, as it is in PFIC3 patients. New developments in the treatment of canalicular transport defects by using nuclear receptors as a target, enhancing the expression of the mutated transporter protein by employing chaperones, or by mutation specific therapy show substantial promise. This review will focus on the therapy that is currently available as well as on those developments that are likely to influence clinical practice in the near future.