Evaluation of the child with suspected mitochondrial liver disease

Considerations for liver transplantation in deoxyguanosine kinase deficiency: A case series and review of the literature

BACKGROUND

Deoxyguanosine kinase (DGUOK) deficiency is a rare mitochondrial disorder characterized by early onset liver failure and varying degrees of neurologic dysfunction. Patients typically present during infancy with progressive hepatic dysfunction leading to liver failure, which can precede neurologic deterioration. Outcomes posttransplantation are historically worse than average and the role of liver transplantation remains controversial. These factors, in combination with the increasing number of patients being diagnosed via molecular genetic testing, may impede waitlist access.

METHODS

We report our single-center experience with three patients with DGUOK deficiency, all of whom were considered for transplant. We review the current literature regarding management and discuss the role of liver transplantation in DGUOK deficiency-associated liver failure.

RESULTS

Two patients presented with hypoglycemia, conjugated hyperbilirubinemia, and lactic acidosis within the first week of life, were diagnosed with DGUOK deficiency prior to 2 months of age and had severe neurologic involvement. The third patient presented in later infancy was diagnosed with DGUOK deficiency at 18 months of age and had minimal neurologic involvement. All three patients were considered for transplant, though only two patients were listed. All three died from complications of end-stage liver failure prior to liver transplantation between the ages of 5-20 months.

CONCLUSION

Selection for liver transplantation in DGUOK deficiency is complex, requiring a multidisciplinary team approach. Recent data suggest that liver transplantation can be successful in select patients with absent or mild neurologic manifestations. National databases reporting long-term outcomes posttransplantation are needed.

Protein biomarkers GDF15 and FGF21 to differentiate mitochondrial hepatopathies from other pediatric liver diseases

BACKGROUND

Mitochondrial hepatopathies (MHs) are primary mitochondrial genetic disorders that can present as childhood liver disease. No recognized biomarkers discriminate MH from other childhood liver diseases. The protein biomarkers growth differentiation factor 15 (GDF15) and fibroblast growth factor 21 (FGF21) differentiate mitochondrial myopathies from other myopathies. We evaluated these biomarkers to determine if they discriminate MH from other liver diseases in children.

METHODS

Serum biomarkers were measured in 36 children with MH (17 had a genetic diagnosis); 38 each with biliary atresia, α1-antitrypsin deficiency, and Alagille syndrome; 20 with NASH; and 186 controls.

RESULTS

GDF15 levels compared to controls were mildly elevated in patients with α1-antitrypsin deficiency, Alagille syndrome, and biliary atresia-young subgroup, but markedly elevated in MH (p<0.001). FGF21 levels were mildly elevated in NASH and markedly elevated in MH (p<0.001). Both biomarkers were higher in patients with MH with a known genetic cause but were similar in acute and chronic presentations. Both markers had a strong performance to identify MH with a molecular diagnosis with the AUC for GDF15 0.93±0.04 and for FGF21 0.90±0.06. Simultaneous elevation of both markers >98th percentile of controls identified genetically confirmed MH with a sensitivity of 88% and specificity of 96%. In MH, independent predictors of survival without requiring liver transplantation were international normalized ratio and either GDF15 or FGF21 levels, with levels <2000 ng/L predicting survival without liver transplantation (p<0.01).

CONCLUSIONS

GDF15 and FGF21 are significantly higher in children with MH compared to other childhood liver diseases and controls and, when combined, were predictive of MH and had prognostic implications.

Differential requirements for mitochondrial electron transport chain components in the adult murine liver

Mitochondrial electron transport chain (ETC) dysfunction due to mutations in the nuclear or mitochondrial genome is a common cause of metabolic disease in humans and displays striking tissue specificity depending on the affected gene. The mechanisms underlying tissue-specific phenotypes are not understood. Complex I (cI) is classically considered the entry point for electrons into the ETC, and in vitro experiments indicate that cI is required for basal respiration and maintenance of the NAD+/NADH ratio, an indicator of cellular redox status. This finding has largely not been tested in vivo. Here, we report that mitochondrial complex I is dispensable for homeostasis of the adult mouse liver; animals with hepatocyte-specific loss of cI function display no overt phenotypes or signs of liver damage, and maintain liver function, redox and oxygen status. Further analysis of cI-deficient livers did not reveal significant proteomic or metabolic changes, indicating little to no compensation is required in the setting of complex I loss. In contrast, complex IV (cIV) dysfunction in adult hepatocytes results in decreased liver function, impaired oxygen handling, steatosis, and liver damage, accompanied by significant metabolomic and proteomic perturbations. Our results support a model whereby complex I loss is tolerated in the mouse liver because hepatocytes use alternative electron donors to fuel the mitochondrial ETC.

Mitochondrial Hepatopathy

Mitochondrial hepatopathies are a subset of mitochondrial diseases defined by primary dysfunction of hepatocyte mitochondria leading to a phenotype of hepatocyte cell injury, steatosis, or liver failure. Increasingly, the diagnosis is established by new sequencing approaches that combine analysis of both nuclear DNA and mitochondrial DNA and allow for timely diagnosis in most patients. Despite advances in diagnostics, for most affected children their disorders are relentlessly progressive, and result in substantial morbidity and mortality. Treatment remains mainly supportive; however, novel therapeutics and a more definitive role for liver transplantation hold promise for affected children.

Acute Liver Failure in Children

Acute liver failure (ALF) in children, irrespective of cause, is a rapidly evolving catastrophic clinical condition that results in high mortality and morbidity without prompt identification and intervention. Massive hepatocyte necrosis impairs the synthetic, excretory, and detoxification abilities of the liver, with resultant coagulopathy, jaundice, metabolic disturbance, and encephalopathy. Extrahepatic organ damage, multiorgan failure, and death result from circulating inflammatory mediators released by the hepatocytes undergoing necrosis. There are yet no treatment options available for reversing or halting hepatocellular necrosis, thus current therapy focuses on supporting failing organs and preventing life threatening complications pending either spontaneous liver recovery or transplantation. The aims of this review are to define pediatric acute liver failure (PALF), understand the pathophysiologic processes that lead to multiorgan failure, to describe the consequences of a failing liver on extrahepatic organs, to enumerate the critical care challenges encountered during PALF management, and to describe pharmacologic and extracorporeal options available to support a critically ill child with ALF in the intensive care unit.

Mitochondrial hepatopathy: Respiratory chain disorders- ‘breathing in and out of the liver’

Mitochondria, the powerhouse of a cell, are closely linked to the pathophysiology of various common as well as not so uncommon disorders of the liver and beyond. Evolution supports a prokaryotic descent, and, unsurprisingly, the organelle is worthy of being labeled an organism in itself. Since highly metabolically active organs require a continuous feed of energy, any dysfunction in the structure and function of mitochondria can have variable impact, with the worse end of the spectrum producing catastrophic consequences with a multisystem predisposition. Though categorized a hepatopathy, mitochondrial respiratory chain defects are not limited to the liver in time and space. The liver involvement is also variable in clinical presentation as well as in age of onset, from acute liver failure, cholestasis, or chronic liver disease. Other organs like eye, muscle, central and peripheral nervous system, gastrointestinal tract, hematological, endocrine, and renal systems are also variably involved. Diagnosis hinges on recognition of subtle clinical clues, screening metabolic investigations, evaluation of the extra-hepatic involvement, and role of genetics and tissue diagnosis. Treatment is aimed at both circumventing the acute metabolic crisis and long-term management including nutritional rehabilitation. This review lists and discusses the burden of mitochondrial respiratory chain defects, including various settings when to suspect, their evolution with time, including certain specific disorders, their tiered evaluation with diagnostic algorithms, management dilemmas, role of liver transplantation, and the future research tools.

Movement Disorders and Liver Disease

The association of movement disorders with structural or functional hepatic disease occurs in three principal scenarios: (1) combined involvement of both organ systems from a single disease entity, (2) nervous system dysfunction resulting from exposure to toxic compounds in the setting of defective hepatic clearance, or (3) hepatic and/or neurological injury secondary to exposure to exogenous drugs or toxins. An important early step in the workup of any patient with combined movement disorders and liver disease is the exclusion of Wilson's disease. Diagnostic delay remains common for this treatable disorder, and this has major implications for patient outcomes. Thereafter, a structured approach integrating variables such as age of onset, tempo of progression, nature and severity of liver involvement, movement disorder phenomenology, exposure to drugs/toxins and laboratory/neuroimaging findings is key to ensuring timely diagnosis and disease‐specific therapy. Herein, we provide an overview of disorders which may manifest with a combination of movement disorders and liver disease, structured under the three headings as detailed above. In each section, the most common disorders are discussed, along with important clinical pearls, suggested diagnostic workup, differential diagnoses and where appropriate, treatment considerations.

Pediatric liver diseases and ocular changes: What hepatologists and ophthalmologists should know and share with each other

Several rare pediatric liver disorders are accompanied by ophthalmic signs whose awareness and early identification may be of value in confirming/accelerating their diagnosis. Many of these signs are asymptomatic and can only be detected with an ophthalmological examination. Corneal signs are described in patients with Wilson's disease, Alagille's syndrome and some liver storage diseases. Cataract plays an important role to diagnose galactosemia. Retinal involvement is seen in some peroxisomal disorders (e.g. Zellweger's syndrome), in mucopolysaccharidoses (pigmentary retinopathy), and in Niemann-Pick disease (macular cherry red spot). In mucopolysaccharidoses optic nerve can be involved as optic atrophy secondary to pigmentary retinopathy or to chronic papilledema. Children with neonatal cholestasis due to hypopituitarism may present septo-optic dysplasia. Several infectious agents have an ophthalmological/hepatic involvement in the fetal life and/or thereafter. Some mitochondrial liver diseases, such as Pearson's syndrome, present pigmentary retinopathy and a chronic progressive external ophthalmoplegia. Finally, some drugs while protecting the liver may damage the ocular system as seen with long-term glucocorticoids and Nitisinone administration. This review provides a synopsis of those conditions that hepatologists and ophthalmologists should share among themselves to better take care of patients. Synoptic tables are presented to facilitate the mutual understanding of the issues.

An Overview of Liver Transplant Pathology: Data from a Tertiary Referral Centre in Western India

INTRODUCTION AND AIM

1. Study of liver explants - Etiologic types of end-stage chronic liver disease (ESCLD) and acute liver failure (ALF) in adults and children. 2. Assessment of donor steatosis and incidental granulomas. 3. Post-transplant liver biopsies.

MATERIAL AND METHODS

Specimens of 180 explant hepatectomies, 173 donor wedge and 30 core liver biopsies, and 58 post transplant liver biopsies received in our department from April 2013 to March 2017.

RESULTS

1. Most common causes of ESCLD in adults were: alcohol related (30.32%), hepatitis virus related (18.71%) and non-alcoholic steatohepatitis related (18.06%); and in children ≤ 12 years were: biliary atresia (27.27%), autoimmune disease (18.18%) and Wilson's disease (18.18%). Most common causes of ALF in adults and children were anti-tubercular therapy induced and idiopathic respectively. 2. Prevalence rate of moderate steatosis (between 30-60%) was 4.28%. Incidental granulomas were seen in 5 cases. 3. Most common diagnoses of post-transplant biopsies in adults included acute cellular rejection (ACR) (36.17%), recurrence of viral disease (8.51%) and moderate non-specific portal triaditis (8.51%). Among children ≤ 12 years, most common diagnoses included unremarkable liver parenchyma, ACR and ischemia/reperfusion injury.

CONCLUSION

1. Alcohol- and hepatitis- virus related ESCLD, and biliary atresia are leading indications for liver transplantation in adults and children respectively. 2. Prevalence of 4.28% of moderate steatosis, is much lower than that documented in western literature. Only 5 cases of incidental granulomas is unexpectedly low in a country endemic for tuberculosis. 3. Most common diagnoses of post-transplant liver biopsies in adults has been acute rejection, which is similar to the findings from much larger published series.

Paediatric fatty liver disease (PeFLD): All is not NAFLD - Pathophysiological insights and approach to management

The recognition of a pattern of steatotic liver injury where histology mimicked alcoholic liver disease, but alcohol consumption was denied, led to the identification of non-alcoholic fatty liver disease (NAFLD). Non-alcoholic fatty liver disease has since become the most common chronic liver disease in adults owing to the global epidemic of obesity. However, in paediatrics, the term NAFLD seems incongruous: alcohol consumption is largely not a factor and inherited metabolic disorders can mimic or co-exist with a diagnosis of NAFLD. The term paediatric fatty liver disease may be more appropriate. In this article, we summarise the known causes of steatosis in children according to their typical, clinical presentation: i) acute liver failure; ii) neonatal or infantile jaundice; iii) hepatomegaly, splenomegaly or hepatosplenomegaly; iv) developmental delay/psychomotor retardation and perhaps most commonly; v) the asymptomatic child with incidental discovery of abnormal liver enzymes. We offer this model as a means to provide pathophysiological insights and an approach to management of the ever more complex subject of fatty liver.

NBAS mutations cause acute liver failure: when acetaminophen is not a culprit

Background

Pediatric acute-liver-failure due to acetaminophen (APAP) administration at therapeutic dosage is rare, while viral infections and metabolic defects are the prevalent causes. Yet, as acetaminophen is routinely used in febrile illnesses, it may be mistakenly held responsible for the acute liver damage.

Case presentation

An 11 month old boy had been on acetaminophen for 10 days (total dose 720 mg = 72 mg/kg) when he developed acute-liver-failure with encephalopathy. As he rapidly improved on N-acetylcysteine (NAC) infusion, it was concluded that chronic acetaminophen administration in an infant had lead to acute-liver-failure even at therapeutic doses, that N-acetylcysteine infusion had been life-saving and should be immediately started in similar circumstances. The child, however, had two further episodes of acute liver damage over a 34-month period, without having been given acetaminophen, as the parents carefully avoided using it. His clinical, laboratory and radiological findings between the acute episodes were unremarkable. His features and skeletal surveys were not suggestive of a syndromic condition. He then went on to suffer another episode of acute-liver-failure with multi-organ failure, necessitating an urgent liver transplant. All efforts to come to a diagnosis for the causes of his recurrent episodes of liver failure had been unsuccessful, until a biallelic mutation in the NBAS gene was reported to be associated with recurrent acute-liver-failure in children. The boy’s DNA analysis revealed compound heterozygous pathogenic mutations in the NBAS gene. Liver failure episodes in these patients are triggered and worsened by fever, most likely due to thermal susceptibility of hepatocytes, hence APAP, rather than being a culprit, is part of the supportive treatment.

Conclusions

We suggest that, in acute-liver-failure with a history of acetaminophen exposure at therapeutic dosage, clinicians should not be contented with administering NAC, but should consider an alternative etiology, above all if the episodes are recurrent, and actively start supportive and antipyretic treatment while seeking the advice of a specialist unit.

Pediatric Liver Transplantation: Unique Concerns for the Critical Care Team

Liver transplantation originated in children more than 50 years ago, and these youngest patients, while comprising the minority of liver transplant recipients nationwide, can have some of the best and most rewarding outcomes. The indications for liver transplantation in children are generally more diverse than those seen in adult patients. This diversity in underlying cause of disease brings with it increased complexity for all who care for these patients. Children, still being completely dependent on others for survival, also require a care team that is able and ready to work with parents and family in addition to the patient at the center of the process. In this review, we aim to discuss diagnoses of particular uniqueness or importance to pediatric liver transplantation. We also discuss the evaluation of a pediatric patient for liver transplant, the system for allocating them a new liver, and also touch on postoperative concerns that are unique to the pediatric population.

Lactate and Lactate: Pyruvate Ratio in the Diagnosis and Outcomes of Pediatric Acute Liver Failure

OBJECTIVES

To assess the accuracy of blood lactate and lactate: pyruvate molar ratio (L:P) as a screen for mitochondrial, respiratory chain, or fatty acid oxidation disorders in children with pediatric acute liver failure (PALF); to determine whether serum lactate ≥ 2.5 mmol/L or L:P  ≥ 25 correlated with biochemical variables of clinical severity; and to determine whether lactate or L:P is associated with clinical outcome at 21 days.

STUDY DESIGN

Retrospective review of demographic, clinical, laboratory, and outcome data for PALF study group participants who had lactate and pyruvate levels collected on the same day.

RESULTS

Of 986 participants, 110 had lactate and pyruvate levels collected on the same day. Of the 110, the etiology of PALF was a mitochondrial disorder in 8 (7%), indeterminate in 65 (59%), and an alternative diagnosis in 37 (34%). Lactate, pyruvate, and L:P were similar among the 3 etiologic groups. There was no significant association between the initial lactate or L:P and biochemical variables of clinical severity or clinical outcome at 21 days.

CONCLUSIONS

A serum lactate ≥ 2.5 mmol/L and/or elevated L:P was common in all causes of PALF, not limited to those with a mitochondrial etiology, and did not predict 21-day clinical outcome.

TRIAL REGISTRATION

ClinicalTrials.gov: NCT00986648.

Incidence of Primary Mitochondrial Disease in Children Younger Than 2 Years Presenting With Acute Liver Failure

BACKGROUND

Mitochondrial liver disease (MLD), and in particular mitochondrial DNA (mtDNA) depletion syndrome (MDS) is an important cause of acute liver failure (ALF) in infancy. Early and accurate diagnosis is important because liver transplantation (LT) is often contraindicated. It is unclear which methods are the best to diagnose MLD in the setting of ALF.

OBJECTIVE

The aim of the study was to determine the incidence of MLD in children younger than 2 years with ALF and the utility of routine investigations to detect MLD.

METHODS

Thirty-nine consecutive infants with ALF were admitted to a single unit from 2009 to 2011. All were extensively investigated using an established protocol. Genes implicated in mitochondrial DNA depletion syndrome were sequenced in all cases and tissue mtDNA copy number measured where available.

RESULTS

Five infants (17%) had genetically proven MLD: DGUOK (n = 2), POLG (n = 2), and MPV17 (1). Four of these died, whereas 1 recovered. Two had normal muscle mtDNA copy number and 3 had normal muscle respiratory chain enzymes. An additional 8 children had low hepatic mtDNA copy number but pathogenic mutations were not detected. One of these developed fatal multisystemic disease after LT, whereas 5 who survived remain well without evidence of multisystemic disease up to 6 years later. Magnetic resonance spectroscopy did not distinguish between those with and without MLD.

CONCLUSIONS

Low liver mtDNA copy number may be a secondary phenomenon in ALF.Screening for mtDNA maintenance gene mutations may be the most efficient way to confirm MLD in ALF in the first 2 years of life.

Deep Sequencing Reveals Novel Genetic Variants in Children with Acute Liver Failure and Tissue Evidence of Impaired Energy Metabolism

Background & Aims

The etiology of acute liver failure (ALF) remains elusive in almost half of affected children. We hypothesized that inherited mitochondrial and fatty acid oxidation disorders were occult etiological factors in patients with idiopathic ALF and impaired energy metabolism.

Methods

Twelve patients with elevated blood molar lactate/pyruvate ratio and indeterminate etiology were selected from a retrospective cohort of 74 subjects with ALF because their fixed and frozen liver samples were available for histological, ultrastructural, molecular and biochemical analysis.

Results

A customized next-generation sequencing panel for 26 genes associated with mitochondrial and fatty acid oxidation defects revealed mutations and sequence variants in five subjects. Variants involved the genes ACAD9, POLG, POLG2, DGUOK, and RRM2B; the latter not previously reported in subjects with ALF. The explanted livers of the patients with heterozygous, truncating insertion mutations in RRM2B showed patchy micro- and macrovesicular steatosis, decreased mitochondrial DNA (mtDNA) content <30% of controls, and reduced respiratory chain complex activity; both patients had good post-transplant outcome. One infant with severe lactic acidosis was found to carry two heterozygous variants in ACAD9, which was associated with isolated complex I deficiency and diffuse hypergranular hepatocytes. The two subjects with heterozygous variants of unknown clinical significance in POLG and DGUOK developed ALF following drug exposure. Their hepatocytes displayed abnormal mitochondria by electron microscopy.

Conclusion

Targeted next generation sequencing and correlation with histological, ultrastructural and functional studies on liver tissue in children with elevated lactate/pyruvate ratio expand the spectrum of genes associated with pediatric ALF.

Neonatal acute liver failure

Neonatal acute liver failure (NALF) is a rare disease about which there is little published data; however, NALF is an extremely important condition as it is distinct from acute liver failure seen in older children and adults. First, unlike acute liver failure in older patients, NALF can be diagnosed in an infant with cirrhosis. This is due to the fetal-neonatal continuum of liver disease, or the principle that neonatal liver failure may be the result of a liver disease that began in utero. Further differences exist in the mechanism of disease, diagnostic principles, and the common etiologies of NALF when compared with pediatric and adult acute liver failure. This review will address many of the distinguishing features of NALF and focus on the most common etiologies of NALF, including gestational alloimmune liver disease (GALD), the most common cause of NALF. Additionally, this review will provide insight into the pathogenesis, diagnosis, and treatment of this rare condition. Liver Transplantation 22 677-685 2016 AASLD.

Cirrhosis in children and adolescents: An overview

Several conditions, especially chronic liver diseases, can lead to cirrhosis in children and adolescents. Most cases in clinical practice are caused by similar etiologies. In infants, cirrhosis is most often caused by biliary atresia and genetic-metabolic diseases, while in older children, it tends to result from autoimmune hepatitis, Wilson's disease, alpha-1-antitrypsin deficiency and primary sclerosing cholangitis. The symptoms of cirrhosis in children and adolescents are similar to those of adults. However, in pediatric patients, the first sign of cirrhosis is often poor weight gain. The complications of pediatric cirrhosis are similar to those observed in adult patients, and include gastrointestinal bleeding caused by gastroesophageal varices, ascites and spontaneous bacterial peritonitis. In pediatric patients, special attention should be paid to the nutritional alterations caused by cirrhosis, since children and adolescents have higher nutritional requirements for growth and development. Children and adolescents with chronic cholestasis are at risk for several nutritional deficiencies. Malnutrition can have severe consequences for both pre- and post-liver transplant patients. The treatment of cirrhosis-induced portal hypertension in children and adolescents is mostly based on methods developed for adults. The present article will review the diagnostic and differential diagnostic aspects of end-stage liver disease in children, as well as the major treatment options for this condition.

Diagnosis and management of mitochondrial disease: a consensus statement from the Mitochondrial Medicine Society

PURPOSE

The purpose of this statement is to review the literature regarding mitochondrial disease and to provide recommendations for optimal diagnosis and treatment. This statement is intended for physicians who are engaged in diagnosing and treating these patients.

METHODS

The Writing Group members were appointed by the Mitochondrial Medicine Society. The panel included members with expertise in several different areas. The panel members utilized a comprehensive review of the literature, surveys, and the Delphi method to reach consensus. We anticipate that this statement will need to be updated as the field continues to evolve.

RESULTS

Consensus-based recommendations are provided for the diagnosis and treatment of mitochondrial disease.

CONCLUSION

The Delphi process enabled the formation of consensus-based recommendations. We hope that these recommendations will help standardize the evaluation, diagnosis, and care of patients with suspected or demonstrated mitochondrial disease.

Secondary Mitochondrial Respiratory Chain Defect Can Delay Accurate PFIC2 Diagnosis

Multiple respiratory chain deficiencies represent a common cause of mitochondrial diseases and often result in hepatic failure. There is no gold-standard test for diagnosing mitochondrial disease, and the current diagnosis relies on establishing a consistent pattern of evidence from clinical data, neuroimaging, tissue biopsy, and biochemical investigations. In some patients, the mitochondrial respiratory chain defect (MRCD) diagnosis is confirmed by genetic investigations. In most cases, genetic investigations are not informative and a number of cases remain unexplained.Here, we report on two children presenting with liver disease in whom first investigations suggested MRCD, due to decreased liver respiratory chain activities and decreased mitochondrial DNA copy number. However, sequencing of the genes known to be associated with mitochondrial DNA instability did not identify any pathogenic mutations. Further investigations including exome analysis, biliary bile salt analysis, and/or BSEP immunostaining detected a defect in the bile salt export pump (BSEP). Diagnosis of progressive familial intrahepatic cholestasis type 2 (PFIC2), a hereditary disorder in bile formation due to BSEP deficiency was confirmed by ABCB11 gene sequencing. Deleterious mutations were identified in both patients: one harboring compound heterozygous mutations (p.Arg470*/c.1308+2T>A) and the other homozygous nonsense mutation (p.Tyr354*). This report increases awareness of a possible secondary mitochondrial respiratory chain defect in the liver tissue associated with other underlying causes such as PFIC2.