Inborn Errors of Bile Acid Metabolism

Immunology of bile acids regulated receptors

Bile acids are steroids formed at the interface of host metabolism and intestinal microbiota. While primary bile acids are generated in the liver from cholesterol metabolism, secondary bile acids represent the products of microbial enzymes. Close to 100 different enzymatic modifications of bile acids structures occur in the human intestine and clinically guided metagenomic and metabolomic analyses have led to the identification of an extraordinary number of novel metabolites. These chemical mediators make an essential contribution to the composition and function of the postbiota, participating to the bidirectional communications of the intestinal microbiota with the host and contributing to the architecture of intestinal-liver and -brain and -endocrine axes. Bile acids exert their function by binding to a group of cell membrane and nuclear receptors collectively known as bile acid-regulated receptors (BARRs), expressed in monocytes, tissue-resident macrophages, CD4+ T effector cells, including Th17, T regulatory cells, dendritic cells and type 3 of intestinal lymphoid cells and NKT cells, highlighting their role in immune regulation. In this review we report on how bile acids and their metabolitesmodulate the immune system in inflammations and cancers and could be exploiting for developing novel therapeutic approaches in these disorders.

What's new in pediatric genetic cholestatic liver disease: advances in etiology, diagnostics and therapeutic approaches

PURPOSE OF REVIEW

To highlight recent advances in pediatric cholestatic liver disease, including promising novel prognostic markers and new therapies.

FINDINGS

Identification of additional genetic variants associated with progressive familial intrahepatic cholestasis (PFIC) phenotype and new genetic cholangiopathies, with an emerging role of ciliopathy genes. Genotype severity predicts outcomes in bile salt export pump (BSEP) deficiency, and post-biliary diversion serum bile acid levels significantly affect native liver survival in BSEP and progressive familial intrahepatic cholestasis type 1 (FIC1 deficiency) patients. Heterozygous variants in the MDR3 gene have been associated with various cholestatic liver disease phenotypes in adults. Ileal bile acid transporter (IBAT) inhibitors, approved for pruritus in PFIC and Alagille Syndrome (ALGS), have been associated with improved long-term quality of life and event-free survival.

SUMMARY

Next-generation sequencing (NGS) technologies have revolutionized diagnostic approaches, while discovery of new intracellular signaling pathways show promise in identifying therapeutic targets and personalized strategies. Bile acids may play a significant role in hepatic damage progression, suggesting their monitoring could guide cholestatic liver disease management. IBAT inhibitors should be incorporated early into routine management algorithms for pruritus. Data are emerging as to whether IBAT inhibitors are impacting disease biology and modifying the natural history of the cholestasis.

Navigating cholestasis: identifying inborn errors of bile acid metabolism for precision diagnosis

Inborn errors of bile acid metabolism (IEBAM) cause cholestasis during the neonatal period, and 8 types of IEBAM have been reported to date. IEBAM accounts for approximately 2% of cases of cholestasis of unknown cause. As only 10 patients have been identified in Japan, IEBAM presents diagnostic challenges due to the similarity of clinical symptoms with biliary atresia, thus necessitating precise differentiation to avoid unnecessary invasive procedures. Laboratory tests in IEBAM are characterized by normal γ-glutamyltransferase (GGT) and serum total bile acid (STBA) levels despite the presence of cholestasis; therefore, measuring STBA and GGT is essential to distinguishing biliary atresia from IEBAM. With suspected IEBAM, liquid chromatography-mass spectrometry (LC/MS) analysis of urinary bile acids is needed to optimize diagnostic and therapeutic efficacy and avoid open cholangiography and initiate treatment for primary bile acids such as cholic acid or chenodeoxycholic acid. This prospective report aims to increase awareness of IEBAM by highlighting the characteristics of general blood test and bile acid profiles from LC/MS analyses of blood, urine, and stool samples.

Intrahepatic Cholangiolitis in Cystic Fibrosis (ICCF): An Under-Appreciated Cause of Persistent Cholestasis in Infancy

Liver histology in infants with cystic fibrosis (CF) and persistent cholestasis is seldom reported in detail. We extend previous observation of a distinctive intrahepatic cholangiopathy (ICCF) to 3 additional infants homozygous for CFTR pathological variants and a fourth infant with a heterozygous CFTR variant, summarizing our experience in 10 infants with CFTR variants and persistent cholestasis. Cholangiograms demonstrate abnormal extrahepatic ducts in 2 infants with CF, 1 with uniform dilatation interpreted as a choledochal cyst and the other with narrow patent ducts. Liver histology in 3 CF homozygotes had prominent ductular reaction with a focally destructive cholangiolitis (inflammation of small bile ducts). The CFTR heterozygote had generalized portal edema with ductular reaction and paucity but no cholangitis. Cholestasis slowly subsided in all infants. ICCF is characterized by severe ductular reaction, prominent cholangiocyte injury, and multifocal necrotizing cholangiolitis. Local aggregates of portal ceroid might suggest previous bile leakage from damaged ducts. ICCF in liver biopsies from infants with cystic fibrosis and persistent cholestasis is unrelated to the specific CFTR genotype. Liver biopsy findings and intraoperative cholangiogram help rule out biliary atresia. ICCF is an early manifestation of CF, a likely prototype for pathogenesis of cystic fibrosis liver disease later in life.

Dried blood spot-based newborn screening for bile acid synthesis disorders, Zellweger spectrum disorder, and Niemann-Pick type C1 by detection of bile acid metabolites

OBJECTIVE

To examine whether it is possible to screen for bile acid synthesis disorders (BASDs) including peroxisome biogenesis disorder 1a (PBD1A) and Niemann-Pick type C1 (NPC1) at the time of newborn mass screening by measuring the intermediary metabolites of bile acid (BA) synthesis.

METHODS

Patients with 3β-hydroxy-ΔSuchy et al. (2021)5-C27-steroid dehydrogenase/isomerase (HSD3B7) deficiency (n = 2), 3-oxo-ΔPandak and Kakiyama (n.d.)4-steroid 5β-reductase (SRD5B1) deficiency (n = 1), oxysterol 7α-hydroxylase (CYP7B1) deficiency (n = 1), PBD1A (n = 1), and NPC1 (n = 2) with available dried blood spot (DBS) samples collected in the neonatal period were included. DBSs from healthy neonates at 4 days of age (n = 1055) were also collected for the control. Disease specific BAs were measured by newly optimized liquid chromatography-tandem mass spectrometry with short run cycle (5-min/run). The results were validated by comparing with those obtained by the conventional condition with longer run cycle (76-min/run).

RESULTS

In healthy specimens, taurocholic acid and cholic acid were the two major BAs which constituted approximately 80% in the measured BAs. The disease marker BAs presented <10%. In BASDs, the following BAs were determined for the disease specific markers: Glyco/tauro 3β,7α,12α-trihydroxy-5-cholenoic acid 3-sulfate for HSD3B7 deficiency (>70%); glyco/tauro 7α,12α-dihydroxy-3-oxo-4-cholenoic acid for SRD5B1 deficiency (54%); tauro 3β-hydroxy-5-cholenoic acid 3-sulfate for CYP7B1 deficiency (94%); 3α,7α,12α-trihydroxy-5β-cholestanoic acid for PBD1A (78%); and tauro 3β,7β-dihydroxy-5-cholenoic acid 3-sulfate for NPC1 (26%). *The % in the parenthesis indicates the portion found in the patient's specimen.

CONCLUSIONS

Early postnatal screening for BASDs, PBD1A and NPC1 is feasible with the described DBS-based method by measuring disease specific BAs. The present method is a quick and affordable test for screening for these inherited diseases.

Novel mutation in the HSD3B7 gene causes bile acid synthetic disorder and presents as recurrent liver failure in early childhood

Bile acid synthetic disorders are rare inborn errors of metabolism, and presentations include neonatal cholestasis, neurological disease or deficiency of fat-soluble vitamins. Affected patients fail to produce standard bile acids but accumulate unusual bile acids and intermediates, resulting in liver failure and complications. Most of them improve with bile acid supplementation, but delaying initiating treatment is detrimental to the outcome.A young child presented to us with recurrent episodes of acute liver failure. In the first episode, both coagulopathy and encephalopathy improved on supportive treatment, but the aetiological evaluation was inconclusive. During the second presentation, whole-exome sequencing was sent, identifying a compound heterozygous novel mutation in the 3-β-hydroxysteroid dehydrogenase type 7 gene leading to bile acid synthetic defect.

Potential mechanisms of Lian-Zhi-Fan solution for TNBS-induced ulcerative colitis in rats via a metabolomics approach

Lian-Zhi-Fan (LZF) decoction is a hospital-prescribed traditional Chinese medicine botanical drug prepared by the fermentation of decocted Coptidis Rhizome (Huanglian), Gardeniae Fructus (Zhizi), and alum (Baifan). It has been used clinically in China for the treatment of anal fistula, perianal abscess, ulcerative colitis (UC), and other anorectal diseases for hundreds of years. However, due to the complexity of traditional Chinese medicine, the potential mechanisms of LZF in the treatment of UC have remained unknown. This study primarily investigated the remarkable pharmacological effects of LZF on TNBS-induced UC rats. To explore the complex targets and regulatory mechanisms of metabolic networks under LZF intervention, a metabolomics approach mediated by HPLC/Q-TOF-MS analysis was used to screen the different metabolites and their metabolic pathways in the serum in order to characterize the possible anti-UC mechanisms of LZF. After rectal administration of LZF for seven consecutive days, significant amelioration effects on body weight loss, DAI score, and colon inflammation were found in UC rats. Based on this, further metabolomics identified 14 potential biomarkers in the treatment of UC with LZF, of which five possessed diagnostic significance: L-alanine, taurocholic acid, niacinamide, cholic acid, and L-valine. These metabolites are mainly involved in 12 metabolic pathways, including nicotate and nicotinamide metabolism, glycospholipid metabolism, arginine and proline metabolism, primary bile acid biosynthesis, and pantothenate and CoA biosynthesis. These metabolic pathways suggest that LZF ameliorates UC by regulating amino acid metabolism, fat metabolism, and energy production. This study provides a useful approach for exploring the potential mechanisms of herbal prescription in UC treatment mediated by metabolomics.

Odevixibat: a promising new treatment for progressive familial intrahepatic cholestasis

INTRODUCTION

Progressive familial intrahepatic cholestasis (PFIC) refers to a group of heterogeneous, mostly autosomal recessive disorders resulting from the inability to properly form and excrete bile from hepatocytes. The resulting shared phenotype is one of hepatocellular cholestasis. Clinical management targeting refractory itch and surgical interventions to interrupt the enterohepatic circulation are often pursued with variable efficacy. Recent development of the family of IBAT inhibitor therapeutics has introduced a novel tool in the armamentarium for the treatment of PFIC.

AREAS COVERED

Data from Phase 3 and 3 clinical trials were reviewed. The primary endpoints in most studies included effect on pruritus, serum bile acid levels, and quality of life metrics, with the duration of the study ranging between 24 and 72 weeks. Most common adverse events included diarrhea, vomiting, and elevation in transaminases.

EXPERT OPINION

IBAT inhibition with therapeutics such as odevibixat have shown that it is well-tolerated and efficacious in mitigating itch and reducing serum bile acid levels. While the few early published trials with odevixibat have shown good efficacy, what remains to be seen is long-term, sustainable improvement and if or how these medications will supplement or replace the current medical and surgical therapies available for managing PFIC disorders.

Liver transplantation in an infant with cerebrotendinous xanthomatosis, cholestasis, and rapid evolution of liver failure

BACKGROUND

Cerebrotendinous xanthomatosis (CTX) is a disorder of bile acid (BA) metabolism due to biallelic mutations in CYP27A1. The deposition of cholesterol and cholestanol in multiple tissues results, manifesting as neurologic disease in adults or older children. Neonatal cholestasis (NC) as a presentation of CTX is rare; it may self-resolve or persist, evolving to require liver transplantation (LT).

METHODS

We present in the context of similar reports an instance of CTX manifest as NC and requiring LT.

RESULTS

A girl aged 4mo was evaluated for NC with normal serum gamma-glutamyl transpeptidase activity. An extensive diagnostic work-up, including liver biopsy, identified no etiology. Rapid progression to end-stage liver disease required LT aged 5mo. The explanted liver showed hepatocyte loss and micronodular cirrhosis. Bile salt export pump (BSEP), encoded by ABCB11, was not demonstrable immunohistochemically. Both severe ABCB11 disease and NR1H4 disease-NR1H4 encodes farsenoid-X receptor, necessary for ABCB11 transcription-were considered. However, selected liver disorder panel sequencing and mass-spectrometry urinary BA profiling identified CTX, with homozygosity for the predictedly pathogenic CYP27A1 variant c.646G > C p.(Ala216Pro). Variation in other genes associated with intrahepatic cholestasis was not detected. Immunohistochemical study of the liver-biopsy specimen found marked deficiency of CYP27A1 expression; BSEP expression was unremarkable. Aged 2y, the girl is free from neurologic disease.

CONCLUSIONS

Bile acid synthesis disorders should be routinely included in the NC/"neonatal hepatitis" work-up. The mutually supportive triple approach of BA profiling, immunohistochemical study, and genetic analysis may optimally address diagnosis in CTX, a treatable disease with widely varying presentation.

Congenital Bile Acid Synthesis Defect Type 3 With Severe Neonatal Cholestasis

Congenital bile acid synthesis defect type 3 is a rare metabolic liver disease with only eight patients reported in literature. We describe clinical, pathological and molecular features for a ninth patient. A 4-month-old infant presented to us with conjugated hyperbilirubinemia. His liver biopsy revealed giant cell change, steatosis, and activity with diffuse fibrosis. Immunostaining with bile salt export pump showed preserved canalicular pattern and γ-glutamyl transferase 1 staining showed unusual complete membranous pattern. Genetic workup revealed homozygous single base pair duplication in exon 3 of the CYP7B1 gene. He succumbed to liver disease at 7 months of age.

Cholestatic liver diseases of genetic etiology: Advances and controversies

With the application of modern investigative technologies, cholestatic liver diseases of genetic etiology are increasingly identified as the root cause of previously designated "idiopathic" adult and pediatric liver diseases. Here, we review advances in the field enhanced by a deeper understanding of the phenotypes associated with specific gene defects that lead to cholestatic liver diseases. There are evolving areas for clinicians in the current era specifically regarding the role for biopsy and opportunities for a "sequencing first" approach. Risk stratification based on the severity of the genetic defect holds promise to guide the decision to pursue primary liver transplantation versus medical therapy or nontransplant surgery, as well as early screening for HCC. In the present era, the expanding toolbox of recently approved therapies for hepatologists has real potential to help many of our patients with genetic causes of cholestasis. In addition, there are promising agents under study in the pipeline. Relevant to the current era, there are still gaps in knowledge of causation and pathogenesis and lack of fully accepted biomarkers of disease progression and pruritus. We discuss strategies to overcome the challenges of genotype-phenotype correlation and draw attention to the extrahepatic manifestations of these diseases. Finally, with attention to identifying causes and treatments of genetic cholestatic disorders, we anticipate a vibrant future of this dynamic field which builds upon current and future therapies, real-world evaluations of individual and combined therapeutics, and the potential incorporation of effective gene editing and gene additive technologies.

Biallelic Mutations in Ubiquitin-Specific Peptidase 53 (USP53) Causing Progressive Intrahepatic Cholestasis. Report of a Case With Review of Literature

Whole-exome sequencing studies have recently identified novel genes implicated in normal- or low-GGT pediatric cholestasis including ubiquitin-specific peptidase 53 (USP53). We identified novel biallelic mutations in the USP53 gene in a 7-month-old infant with pruritus and progressive intrahepatic cholestasis. His liver biopsy showed portal and perivenular fibrosis with bland bilirubinostasis. His parents were asymptomatic heterozygous for the same mutation. He is currently on vitamin supplements and cholestyramine and his family has also been counseled for liver transplantation. Our report confirms that patients with biallelic mutation in USP53 develop cholestatic liver disease.

Prognosis and clinical characteristics of patients with 3β-hydroxy-Δ5-C27-steroid dehydrogenase deficiency diagnosed in childhood: A systematic review of the literature

OBJECTIVES

3β-hydroxy-Δ5-C27-steroid dehydrogenase deficiency is a rare autosomal recessive condition. So far fewer than 100 cases have been reported and the factors affecting the prognosis are not yet established. The objective of this study is to explore a possible prediction of the outcome of this rare condition.

METHODS

This review was undertaken and reported in accordance with the preferred reporting items for systematic review and meta-analyses guidelines. Demographics, clinical features, gene data, treatment strategies and prognoses at the last follow-up were extracted and summarized. Patients were divided into 2 groups (alive with native liver and liver transplantation/died). Risk factors for the different clinical features were identified.

RESULTS

87 patients that were taken from 7 case reports and 9 case series were included. 38 (38/63, 63.0%) of them presented initial symptoms when they were younger than 1 month and 55 (55/63, 87.3%) less than 1 year. There is a larger proportion of patients younger than 1 month or 1 year at the age of symptom onset in the liver transplantation /died group than patients in alive with the native liver group. The majority of patients (53/62, 85.5%) were diagnosed before the age of 5 year. In all cases, 65 (predicted) pathogenic variants have been identified. Over 70% of patients carried an HSD3B7 variant on exon 1, 4, 5 or 6. 71 (81.6%) were alive at the last follow-up, 16 (18.4%) underwent liver transplantation or died. No significance was found between the group alive with native liver and group liver transplantation /died.

CONCLUSION

Age of onset of the symptoms may be a potential factor that determines the outcome of patients with 3β-HSD deficiency, patients presented with symptoms and signs at an age younger than 1 month or even 1 year may have a worse prognosis. Since there is no difference between clinical outcome and zygosity of gene mutation, we recommend a further study about any possible relationship between mutation site and clinical characteristics or prognosis.

Diagnostic approach to neonatal and infantile cholestasis: A position paper by the SIGENP liver disease working group

Neonatal and infantile cholestasis (NIC) can represent the onset of a surgically correctable disease and of a genetic or metabolic disorder worthy of medical treatment. Timely recognition of NIC and identification of the underlying etiology are paramount to improve outcomes. Upon invitation by the Italian National Institute of Health (ISS), an expert working grouped was formed to formulate evidence-based positions on current knowledge about the diagnosis of NIC. A systematic literature search was conducted to collect evidence about epidemiology, etiology, clinical aspects and accuracy of available diagnostic tests in NIC. Evidence was scored using the GRADE system. All recommendations were approved by a panel of experts upon agreement of at least 75% of the members. The final document was approved by all the panel components. This position document summarizes the collected statements and defines the best-evidence diagnostic approach to cholestasis in the first year of life.

Genetic spectrum and clinical characteristics of 3β-hydroxy-Δ5-C27-steroid oxidoreductase (HSD3B7) deficiency in China

BACKGROUND

Biallelic variants in HSD3B7 cause 3β-hydroxy-Δ5-C27-steroid oxidoreductase (HSD3B7) deficiency, a life-threatening but treatable liver disease. The goal of this study was to obtain detailed information on the correlation between the genotype and phenotype of HSD3B7 deficiency and to report on responses to primary bile acid therapy.

METHODS

The medical records of a cohort of 39 unrelated patients with genetically and biochemically confirmed HSD3B7 deficiency were examined to determine whether there exist genotype-phenotype relationships in this bile acid synthesis disorder.

RESULTS

In all, 34 of the 44 variants identified in HSD3B7 were novel. A total of 32 patients presented early with neonatal cholestasis, and 7 presented after 1-year of age with liver failure (n = 1), liver cirrhosis (n = 3), cholestasis (n = 1), renal cysts and abnormal liver biochemistries (n = 1), and coagulopathy from vitamin K1 deficiency and abnormal liver biochemistries (n = 1). Renal lesions, including renal cysts, renal stones, calcium deposition and renal enlargement were observed in 10 of 35 patients. Thirty-three patients were treated with oral chenodeoxycholic acid (CDCA) resulting in normalization of liver biochemistries in 24, while 2 showed a significant clinical improvement, and 7 underwent liver transplantation or died. Remarkably, renal lesions in 6 patients resolved after CDCA treatment, or liver transplantation. There were no significant correlations between genotype and clinical outcomes.

CONCLUSIONS

In what is the largest cohort of patients with HSD3B7 deficiency thus far studied, renal lesions were a notable clinical feature of HSD3B7 deficiency and these were resolved with suppression of atypical bile acids by oral CDCA administration.

Dynamics of the enterohepatic circulation of bile acids in healthy humans

Regulation of bile acid metabolism is normally discussed as the regulation of bile acid synthesis, which serves to compensate for intestinal loss in order to maintain a constant pool size. After a meal, bile acids start cycling in the enterohepatic circulation. Farnesoid X receptor-dependent ileal and hepatic processes lead to negative feedback inhibition of bile acid synthesis. When the intestinal bile acid flux decreases, the inhibition of synthesis is released. The degree of inhibition of synthesis and the mechanism and degree of activation are still unknown. Moreover, in humans, a biphasic diurnal expression pattern of bile acid synthesis has been documented, indicating maximal synthesis around 3 PM and 9 PM. Quantitative data on the hourly synthesis schedule as compensation for intestinal loss are lacking. In this review, we describe the classical view on bile acid metabolism and present alternative concepts that are based on the overlooked feature that bile acids transit through the enterohepatic circulation very rapidly. A daily profile of the cycling and total bile acid pool sizes and potential controlled and uncontrolled mechanisms for synthesis are predicted. It remains to be elucidated by which mechanism clock genes interact with the Farnesoid X receptor-controlled regulation of bile acid synthesis. This mechanism could become an attractive target to enhance bile acid synthesis at night, when cholesterol synthesis is high, thus lowering serum LDL-cholesterol.

Cholestasis Due to USP53 Deficiency

OBJECTIVES

Although a number of genetic forms of cholestasis have been identified, the genetic etiology of disease remains unidentified in a subset of cholestasis patients.

METHODS

Whole exome sequencing (WES) was performed in DNA from patients diagnosed with cholestasis, at different points on the continuum from progressive familial intrahepatic cholestasis to benign recurrent intrahepatic cholestasis, in whom no disease mutations in known cholestasis genes had been identified. Candidate genes were then assessed in a larger patient sample, by targeted next-generation sequencing (NGS). Disease features at presentation and follow-up were collected from available medical records.

RESULTS

By WES, we identified 3 patients with homozygous mutations in USP53. Screening of USP53 in a larger set of patients identified 4 additional patients with homozygous mutations in USP53. Six of the 7 patients had deletion mutations, and 1 had a missense mutation; 3 of the patients were siblings, all bearing a deletion that also disrupted neighboring MYOZ2. Age of onset ranged from early infancy to adolescence. Cholestasis tended to be biochemically mild and intermittent, and responsive to medication. Liver fibrosis was, however, present in all 4 patients who were biopsied, and splenomegaly was apparent in 5 of 7 at last ultrasound.

CONCLUSIONS

Two groups recently identified patients with liver disease and mutation in USP53. We have now identified biallelic mutation in USP53 in 7 further patients with cholestasis, from 5 families. Most individuals had evidence of chronic liver disease, and long-term follow-up is recommended.

Bile acids and their receptors in metabolic disorders

Bile acids are a large family of atypical steroids which exert their functions by binding to a family of ubiquitous cell membrane and nuclear receptors. There are two main bile acid activated receptors, FXR and GPBAR1, that are exclusively activated by bile acids, while other receptors CAR, LXRs, PXR, RORγT, S1PR2and VDR are activated by bile acids in addition to other more selective endogenous ligands. In the intestine, activation of FXR and GPBAR1 promotes the release of FGF15/19 and GLP1 which integrate their signaling with direct effects exerted by theother receptors in target tissues. This network is tuned in a time ordered manner by circadian rhythm and is critical for the regulation of metabolic process including autophagy, fast-to-feed transition, lipid and glucose metabolism, energy balance and immune responses. In the last decade FXR ligands have entered clinical trials but development of systemic FXR agonists has been proven challenging because their side effects including increased levels of cholesterol and Low Density Lipoproteins cholesterol (LDL-c) and reduced High-Density Lipoprotein cholesterol (HDL-c). In addition, pruritus has emerged as a common, dose related, side effect of FXR ligands. Intestinal-restricted FXR and GPBAR1 agonists and dual FXR/GPBAR1 agonists have been developed. Here we review the last decade in bile acids physiology and pharmacology.

Dialogs in the assessment of neonatal cholestatic liver disease

Neonatal cholestatic liver disease is rarely encountered by pathologists outside of specialized pediatric centers and navigating the long list of potential diseases can be daunting. However, the differential diagnosis can be rapidly narrowed through open conversations between the pathologist and pediatric gastroenterologist. The dialog should ideally begin before obtaining the liver biopsy and continue through the rendering of the final pathologic diagnosis. Such dialogs are necessary to first ensure the proper handling of the precious sample and then to allow for synthesis of the clinical, laboratory, imaging, and genetic data in the context of the histologic features seen in the liver biopsy. In this review, we aim to provide a broad template on which such dialogs may be based and pitfalls that may be encountered on both the clinical and pathologic sides. This review will focus on non-biliary atresia etiologies of neonatal cholestasis, including select infectious, genetic, and metabolic entities.

Neonatal liver disease

Neonatal liver disease encompasses many diagnoses, including structural and genetic aetiologies. Many have significant health implications requiring long-term specialist treatment including liver transplantation. Jaundice is a common presenting feature. The ability of health-care professionals to differentiate neonatal liver disease from benign diagnoses such as physiological jaundice is very important. Persistent (more than 2 weeks) of conjugated jaundice always warrants investigation. Severe unconjugated jaundice (requiring prolonged phototherapy) should also be promptly investigated. Recent advances in genomics have enabled previously elusive, precise diagnoses in some patients with neonatal liver disease. This review paper discusses the commoner causes, with a focus on early detection and need for referral to paediatric liver services.

The peroxisomal disorder spectrum and Heimler syndrome: Deep phenotyping and review of the literature

The spectrum of peroxisomal disorders is wide and comprises individuals that die in the first year of life, as well as people with sensorineural hearing loss, retinal dystrophy and amelogenesis imperfecta. In this article, we describe three patients; two diagnosed with Heimler syndrome and a third one with a mild-intermediate phenotype. We arrived at these diagnoses by conducting complete ophthalmic (National Eye Institute), auditory (National Institute of Deafness and Other Communication Disorders), and dental (National Institute of Dental and Craniofacial Research) evaluations, as well as laboratory and genetic testing. Retinal degeneration with macular cystic changes, amelogenesis imperfecta, and sensorineural hearing loss were features shared by the three patients. Patients A and C had pathogenic variants in PEX1 and Patient B, in PEX6. Besides analyzing these cases, we review the literature regarding mild peroxisomal disorders, their pathophysiology, genetics, differential diagnosis, diagnostic methods, and management. We suggest that peroxisomal disorders are considered in every child with sensorineural hearing loss and retinal degeneration. These patients should have a dental evaluation to rule out amelogenesis imperfecta as well as audiologic examination and laboratory testing including peroxisomal biomarkers and genetic testing. Appropriate diagnosis can lead to better genetic counseling and management of the associated comorbidities.

Pediatric Cholestatic Liver Disease: Review of Bile Acid Metabolism and Discussion of Current and Emerging Therapies

Cholestatic liver diseases are a significant cause of morbidity and mortality and the leading indication for pediatric liver transplant. These include diseases such as biliary atresia, Alagille syndrome, progressive intrahepatic cholestasis entities, ductal plate abnormalities including Caroli syndrome and congenital hepatic fibrosis, primary sclerosing cholangitis, bile acid synthesis defects, and certain metabolic disease. Medical management of these patients typically includes supportive care for complications of chronic cholestasis including malnutrition, pruritus, and portal hypertension. However, there are limited effective interventions to prevent progressive liver damage in these diseases, leaving clinicians to ultimately rely on liver transplantation in many cases. Agents such as ursodeoxycholic acid, bile acid sequestrants, and rifampicin have been mainstays of treatment for years with the understanding that they may decrease or alter the composition of the bile acid pool, though clinical response to these medications is frequently insufficient and their effects on disease progression remain limited. Recently, animal and human studies have identified potential new therapeutic targets which may disrupt the enterohepatic circulation of bile acids, alter the expression of bile acid transporters or decrease the production of bile acids. In this article, we will review bile formation, bile acid signaling, and the relevance for current and newer therapies for pediatric cholestasis. We will also highlight further areas of potential targets for medical intervention for pediatric cholestatic liver diseases.

Open-label Phase 3 Continuation Study of Cholic Acid in Patients With Inborn Errors of Bile Acid Synthesis

BACKGROUND

In patients with bile acid synthesis disorders (BASD), impairment in the primary bile acid synthetic pathway leads to reduced primary bile acids, upregulated synthesis of cholesterol, and production and accumulation of hepatotoxic atypical bile acids. Primary bile acid therapy downregulates bile acid synthesis, reduces the production of hepatotoxic intermediates, and produces a functional bile acid pool fostering normal liver function.

METHODS

This phase 3, open-label, single-arm study included patients with BASD who had received cholic acid (10-15 mg · kg · day) as part of a previous study, or were newly diagnosed. Efficacy assessments included urinary atypical bile acids; serum liver chemistries; body weight and height. Efficacy analyses compared baseline with worst postbaseline response (primary) or best postbaseline response (sensitivity). Treatment-emergent adverse events (TEAEs) were summarized.

RESULTS

Of 53 total patients (single enzyme defects, n = 41; Zellweger spectrum disorders, n = 12), 22 (42%) were treatment-naïve, and 31 (58%) were on cholic acid from a previous study. Mean age at diagnosis was 55 months, and at present study, baseline was 9 years. Using baseline-to-best postbaseline analyses, statistically significant improvements in urinary bile acids (P = 0.003), height (P < 0.001), and body weight (P < 0.001) were observed. Serum alanine aminotransferase and aspartate aminotransferase levels tended to decrease from baseline in treatment-naïve patients following cholic acid treatment and remained stable in previously treated patients. Treatment-naïve patients improved in all baseline-to-best postbaseline analyses. The most common TEAE was upper respiratory tract infection (17%).

CONCLUSION

Oral cholic acid provides a safe and efficacious short- and long-term therapy for patients with BASD.

Inborn errors of metabolism in the differential diagnosis of fatty liver disease

Nonalcoholic fatty liver disease (NAFLD) has become the most common chronic liver disease across all age groups. Obesity, diabetes, and metabolic syndrome, are the primary causes that are closely linked with the development of NAFLD. However, in young children, rare inborn errors of metabolism are predominant secondary causes of NAFLD. Furthermore, inborn errors of metabolism causing hepatosteatosis are often misdiagnosed as NAFLD in adolescents and adults. Many inborn errors of metabolism are treatable disorders and therefore require special consideration. This review aims to summarize the basic characteristics and diagnostic clues of inborn errors of metabolism associated with fatty liver disease. A suggested clinical and laboratory diagnostic approach is also discussed.

Sterol 27-Hydroxylase Deficiency as a Cause of Neonatal Cholestasis: Report of 2 Cases and Review of the Literature

Introduction: Inborn errors of primary bile acid (BA) synthesis are rare autosomal recessive disorders responsible for 1-2% of cases of neonatal cholestasis. Among them, cerebrotendinous xanthomatosis (CTX) is caused by mutations in the CYP27A1 gene resulting in the impairment of sterol 27-hydroxylase enzyme activity. Patients and Methods: Here we present the study on two siblings with neonatal cholestasis diagnosed with sterol 27-hydroxylase deficiency. The clinical, biochemical, histological, and molecular presentation at the time of diagnosis and detailed follow-up were described. An extensive overview of the literature regarding patients with sterol 27-hydroxylase deficiency presenting with neonatal cholestasis was also provided. Results: Patient 1 presented with cholestatic jaundice since 10 weeks of age and developed the end-stage liver disease requiring liver transplantation at 8 months of age but finally succumbed 3 years post-transplantation due to autoimmune hemolytic anemia and multiorgan failure development. Next-generation sequencing performed post mortem, revealed him to be homozygous for the known pathogenic splicing variant c.1184+1G>A in the CYP27A1 gene. Patient 2 (sibling) presented with cholestatic jaundice since the first day of life. Sanger sequencing of CYP27A1 revealed the same results. Chenodeoxycholic acid treatment was introduced just after diagnosis, at 4 months of age. Fourteen patients with sterol 27-hydroxylase deficiency presenting with neonatal cholestasis were reported in the literature, in most of them presenting as a self-limiting disease. Conclusions: An early recognition and treatment initiation in CTX is essential.

Case Report: Early Treatment With Chenodeoxycholic Acid in Cerebrotendinous Xanthomatosis Presenting as Neonatal Cholestasis

Background: Cerebrotendinous xanthomatosis (CTX) is an inborn disorder of bile acid synthesis which causes progressive accumulation of toxic metabolites in various organs, particularly in brain and tendons. Most cases are diagnosed and treated in the second or third decade of life, when neurological involvement appears. We describe a case of CTX presenting as neonatal cholestasis. Results: The child presented cholestasis at 2 months of life. In the following months jaundice slowly disappeared, with a normalization of bilirubin and aminotransferases, respectively, at 6 and 8 months. A LC-Mass Spectrometry of the urines showed the presence of cholestanepentols glucuronide, which led to the suspicion of cerebrotendinous xanthomatosis. The diagnosis was confirmed by the dosage of cholestanol in serum and the molecular genetic analysis of the CYP27A1 gene. Therapy with chenodeoxycholic acid (CDCA) was started at 8 months and is still ongoing. The child was monitored for 13 years by dosage of serum cholestanol and urinary cholestanepentols. A strictly biochemical and neurological follow up was performed and no sign of neurological impairment was observed. Conclusions: Prompt diagnosis and treatment of CTX presenting as neonatal cholestasis may prevent further neurological impairment.

A practical approach to the pathology of neonatal cholestatic liver disease

Navigating the complexities of interpreting a liver biopsy performed on a neonate with conjugated/direct hyperbilirubinemia can be an arduous task given these biopsies are infrequently encountered. The list of entities is long and yet there are only a few histologic patterns of liver injury. The first step for the pathologist is to determine the histologic pattern, which will guide further inquiry into the useful clinical information to have while evaluating the biopsy. Ultimately, the goal is to identify those conditions that will benefit from early intervention. We begin with a review of biliary development to help understand what findings may be physiologic versus pathologic, particularly in premature infants. Then we review eight cases that cover the three most common histologic patterns of injury in patients with neonatal cholestasis: biliary obstructive, neonatal hepatitis, and paucity of intrahepatic bile ducts. The entities that serve as prototypes for these histologic patterns are covered, including biliary atresia, idiopathic neonatal hepatitis, and Alagille syndrome, along with rarer entities that have histologic overlap. The cases with accompanying tables and algorithms are intended to help place the histologic findings in the context of the overall clinical work-up, including genetic testing.

Inborn Errors of Metabolism and the Gastrointestinal Tract

Inborn errors of metabolism (IEMs) are usually recognized by characteristic neurologic and metabolic manifestations and sometimes by dysmorphism. However, IEMs can present with a wide variety of gastrointestinal manifestations, whether as the primary or a minor clinical symptom. Regardless, gastrointestinal and hepatic manifestations of IEMs are important clinical features that can help identify an underlying defect; these disorders should be taken into consideration as part of a patient's clinical assessment. It is prudent to include metabolic disorders in the differential diagnosis because in some cases, gastrointestinal symptoms may be the only presenting feature in a patient with an underlying IEM.