Fatal deterioration of neurological disease after orthotopic liver transplantation for valproic acid-induced liver damage

POLG-related disorders and their neurological manifestations

The POLG gene encodes the mitochondrial DNA polymerase that is responsible for replication of the mitochondrial genome. Mutations in POLG can cause early childhood mitochondrial DNA (mtDNA) depletion syndromes or later-onset syndromes arising from mtDNA deletions. POLG mutations are the most common cause of inherited mitochondrial disorders, with as many as 2% of the population carrying these mutations. POLG-related disorders comprise a continuum of overlapping phenotypes with onset from infancy to late adulthood. The six leading disorders caused by POLG mutations are Alpers-Huttenlocher syndrome, which is one of the most severe phenotypes; childhood myocerebrohepatopathy spectrum, which presents within the first 3 years of life; myoclonic epilepsy myopathy sensory ataxia; ataxia neuropathy spectrum; autosomal recessive progressive external ophthalmoplegia; and autosomal dominant progressive external ophthalmoplegia. This Review describes the clinical features, pathophysiology, natural history and treatment of POLG-related disorders, focusing particularly on the neurological manifestations of these conditions.

Variants p.Q1236H and p.E1143G in mitochondrial DNA polymerase gamma POLG1 are not associated with increased risk for valproate-induced hepatotoxicity or pancreatic toxicity: A retrospective cohort study of patients with epilepsy

OBJECTIVE

Previous studies have suggested that heterozygous variants p.Q1236H and p.E1143G in mitochondrial DNA polymerase gamma (POLG1) increase the risk for liver injury for patients on valproate (VPA) therapy. We assessed the prevalence of these common variants and seven other pathogenic mutations in POLG1 and determined the occurrence of VPA-induced hepatotoxicity (VHT) or pancreatic toxicity in a cohort of patients with epilepsy.

METHODS

Patients with epilepsy (N = 367) were retrospectively identified from medical record files and screened for mutations in POLG1. Patients who had received VPA monotherapy and carried either of the two variants, p.Q1236H or p.E1143G, without other pathogenic mutations in POLG1 (n = 33, variant group) and patients without these variants (n = 28, nonvariant group) were included in the study. Clinical data on epilepsy, characteristics of VPA treatment, risk factors for VHT, laboratory data on liver and pancreas functions, and adverse effects were collected.

RESULTS

A total of 122 patients had either the POLG1 p.Q1236H (n = 99) or p.E1143G (n = 24) variant in the heterozygous or homozygous state. Transient liver dysfunction was identified in three (n = 33, 9.1%) variant group patients and in one (n = 28, 3.6%) nonvariant group patient (P = 0.62). Mild to moderate elevations in liver enzymes were encountered in both groups. Furthermore, two patients on VPA polytherapy developed acute pancreatitis, and two pediatric patients with heterozygous p.Q1236H variants and mutations in IQSEC2 and GLDC, respectively, had elevated levels of VPA metabolites in urine, elevated plasma glycine, and/or increased acylglycine excretion.

SIGNIFICANCE

POLG1 p.Q1236H and p.E1143G variants could not be identified as statistically significant risk factors for VHT or pancreatic toxicity. We suggest that VPA treatment could be suitable for patients who harbor these common variants in the absence of other pathogenic mutations in POLG1.

Effects of antiepileptic drugs on mitochondrial functions, morphology, kinetics, biogenesis, and survival

OBJECTIVES

Antiepileptic drugs (AEDs) exhibit adverse and beneficial effects on mitochondria, which have a strong impact on the treatment of patients with a mitochondrial disorder (MID) with epilepsy (mitochondrial epilepsy). This review aims at summarizing and discussing recent findings concerning the effect of AEDs on mitochondrial functions and the clinical consequences with regard to therapy of mitochondrial epilepsy and of MIDs in general.

METHODS

Literature review.

RESULTS

AEDs may interfere with the respiratory chain, with non-respiratory chain enzymes, carrier proteins, or mitochondrial biogenesis, with carrier proteins, membrane-bound channels or receptors and the membrane potential, with anti-oxidative defense mechanisms, with morphology, dynamics and survival of mitochondria, and with the mtDNA. There are AEDs of which adverse effects outweigh beneficial effects, such as valproic acid, carbamazepine, phenytoin, or phenobarbital and there are AEDs in which beneficial effects dominate over mitochondrial toxic effects, such as lamotrigine, levetiracetam, gabapentin, or zonisamide. However, from most AEDs only little is known about their interference with mitochondria.

CONCLUSIONS

Mitochondrial epilepsy might be initially treated with AEDs with low mitochondrial toxic potential. Only in case mitochondrial epilepsy is refractory to these AEDs, AEDs with higher mitochondrial toxic potential might be tried. In patients carrying POLG1 mutations AEDs with high mitochondrial toxic potential are contraindicated.

Toxicity of Antiepileptic Drugs to Mitochondria

Some of the side and beneficial effects of antiepileptic drugs (AEDs) are mediated via the influence on mitochondria. This is of particular importance in patients requiring AED treatment for mitochondrial epilepsy. AED treatment in patients with mitochondrial disorders should rely on the known influences of AEDs on these organelles. AEDs may influence various mitochondrial functions or structures in a beneficial or detrimental way. There are AEDs in which the toxic effect outweighs the beneficial effect, such as valproic acid (VPA), carbamazepine (CBZ), phenytoin (PHT), or phenobarbital (PB). There are, however, also AEDs in which the beneficial effect on mitochondria outweighs the mitochondrion-toxic effect, such as gabapentin (GBT), lamotrigine (LTG), levetiracetam (LEV), or zonisamide (ZNS). In the majority of the AEDs, however, information about their influence of mitochondria is lacking. In clinical practice mitochondrial epilepsy should be initially treated with AEDs with low mitochondrion-toxic potential. Only in cases of ineffectivity or severe mitochondrial epilepsy, mitochondrion-toxic AEDs should be given. This applies for AEDs given orally or intravenously.

Acute liver failure after valproate exposure in patients with POLG1 mutations and the prognosis after liver transplantation

Patients with mutations in the POLG1 gene encoding mitochondrial DNA polymerase gamma have an increased risk of valproate-induced liver failure. POLG1 mutations are common, and these patients often suffer from intractable seizures. The role of liver transplantation in the treatment of patients with mitochondrial diseases has been controversial. We studied valproate-induced liver failure associated with POLG1 mutations and the prognosis for these patients after liver transplantation. POLG1 was analyzed in blood DNA, mitochondrial DNA (mtDNA) was quantified in liver samples, and clinical data were collected. Five patients with valproate-induced liver failure associated with POLG1 mutations were retrospectively identified. Three patients were previously suspected to have Wilson's disease. Four patients with homozygous p.W748S and p.E1143G mutations had mtDNA depletion in the liver. One of these patients died before anticipated transplantation; the other 3 patients with liver transplantation have survived 4 to 19 years. Two patients have presented with occasional epileptic seizures, and 1 patient has been seizure-free for 11 years. One patient with a heterozygous p.Q1236H mutation (but without mtDNA depletion in the liver) died suddenly 2 years after liver transplantation. In conclusion, the POLG1 mutation status and the age at presentation of valproate-induced liver failure can affect the prognosis after liver transplantation. A heterozygous POLG1 p.Q1236H mutation was related to valproate-induced liver failure without mtDNA depletion, whereas patients homozygous for POLG1 p.W748S and p.E1143G mutations had mtDNA depletion. An analysis of the POLG1 gene should be performed for all patients with suspected mitochondrial disease before the introduction of valproate therapy, and treatment with valproic acid should be avoided in these patients.

Syndromes associated with mitochondrial DNA depletion

Mitochondrial dysfunction accounts for a large group of inherited metabolic disorders most of which are due to a dysfunctional mitochondrial respiratory chain (MRC) and, consequently, deficient energy production. MRC function depends on the coordinated expression of both nuclear (nDNA) and mitochondrial (mtDNA) genomes. Thus, mitochondrial diseases can be caused by genetic defects in either the mitochondrial or the nuclear genome, or in the cross-talk between the two. This impaired cross-talk gives rise to so-called nuclear-mitochondrial intergenomic communication disorders, which result in loss or instability of the mitochondrial genome and, in turn, impaired maintenance of qualitative and quantitative mtDNA integrity. In children, most MRC disorders are associated with nuclear gene defects rather than alterations in the mtDNA itself.

The mitochondrial DNA depletion syndromes (MDSs) are a clinically heterogeneous group of disorders with an autosomal recessive pattern of transmission that have onset in infancy or early childhood and are characterized by a reduced number of copies of mtDNA in affected tissues and organs. The MDSs can be divided into least four clinical presentations: hepatocerebral, myopathic, encephalomyopathic and neurogastrointestinal. The focus of this review is to offer an overview of these syndromes, listing the clinical phenotypes, together with their relative frequency, mutational spectrum, and possible insights for improving diagnostic strategies.

Gastrointestinal and hepatic manifestations of mitochondrial disorders

Inherited defects of oxidative phosphorylation lead to heterogeneous, often multisystem, mitochondrial diseases. This review highlights those mitochondrial syndromes with prominent gastrointestinal and hepatic symptoms, categorised according to underlying disease mechanism. Mitochondrial encephalopathies with major gastrointestinal involvement include mitochondrial neurogastrointestinal encephalopathy and ethylmalonic encephalopathy, which are each associated with highly specific clinical and metabolic profiles. Mitochondrial hepatopathies are most frequently caused by defects of mitochondrial DNA maintenance and expression. Although mitochondrial disorders are notorious for extreme clinical, biochemical and genetic heterogeneity, there are some pathognomonic clinical and metabolic clues that suggest a specific diagnosis, and these are highlighted. An approach to diagnosis of these complex disorders is presented, together with a genetic classification, including mitochondrial DNA disorders and nuclear-encoded defects of mitochondrial DNA maintenance and translation, OXPHOS complex assembly and mitochondrial membrane lipids. Finally, supportive and experimental therapeutic options for these currently incurable diseases are reviewed, including liver transplantation, allogeneic haematopoietic stem cell transplantation and gene therapy.

Adverse drug reactions induced by valproic acid

Valproic acid is a widely-used first-generation antiepileptic drug, prescribed predominantly in epilepsy and psychiatric disorders. VPA has good efficacy and pharmacoeconomic profiles, as well as a relatively favorable safety profile. However, adverse drug reactions have been reported in relation with valproic acid use, either as monotherapy or polytherapy with other antiepileptic drugs or antipsychotic drugs. This systematic review discusses valproic acid adverse drug reactions, in terms of hepatotoxicity, mitochondrial toxicity, hyperammonemic encephalopathy, hypersensitivity syndrome reactions, neurological toxicity, metabolic and endocrine adverse events, and teratogenicity.

Mitochondrial respiratory chain hepatopathies: role of liver transplantation. A case series of five patients

INTRODUCTION

Orthotopic liver transplantation (OLT) in patients with mitochondrial respiratory chain disorders (MRCD) is controversial because of possible multi-organ involvement.

AIM

To illustrate the clinical diversity of MRCD, the difficulty in making an accurate tissue diagnosis and whether to undertake OLT in five patients with proven MRCD. A review of the reported cases in the literature is presented.

METHODS

Retrospective chart review from 1995 to 2007 at a paediatric liver transplant centre where five children with hepatic MRCD were identified.

RESULTS

Patient 1 was transplanted for 'cryptogenic' cirrhosis. The diagnosis of MRCD was made on the explant. The patient remains well 5 years after transplant. Patient 2 presented with fulminant liver failure at 3 months of age. Although no extrahepatic manifestations were identified, OLT was not considered. Patient 3 presented with recurrent hypoglycaemia and was transplanted for fulminant hepatic failure at 12 months of age. He died of pulmonary hypertension 9 months post OLT. Patient 4 was diagnosed with MRCD at the age of 2 years. Death occurred at the age of 14 years, while listed for combined liver-kidney transplant, after a stroke-like episode following severe sepsis. Patient 5 developed liver failure after valproic acid was instituted for seizures. Mitochondrial DNA depletion syndrome was diagnosed and transplantation was not offered.

CONCLUSION

Hepatic MRCD has a variable presentation. Diagnosis requires the measurement of respiratory chain enzymes on tissue from liver biopsy. Whether to proceed to OLT is a difficult decision given a good outcome in a minority of cases, suggesting that MRCD should not be an absolute contraindication to liver transplantation.

Complete Deletion of a POLG1 Allele in a Patient with Alpers Syndrome

Mutations in the gene encoding the catalytic subunit of polymerase γ (POLG1) are a major cause of human mitochondrial disease. More than 150 different point mutations in the gene have been reported to be disease causing, resulting in a large range of clinical symptoms. Depending on the mutation or combination of mutations, disease onset can occur in early infancy or late in adult life. Here, we describe the use of multiplex ligation-dependent probe amplification (MLPA) analysis to detect deletions within POLG1, which could otherwise go undetected by solely sequencing of the gene. We present a case where an entire POLG1 allele is deleted, with a known pathogenic mutation (W748S) on the remaining allele. The deletion was found in a boy with Alpers syndrome, presenting at 18 months of age with slightly retarded motor development, balance problems, and seizures. Administration of valproic acid (VPA) led to rapidly progressive fatal liver failure in our patient, and we would like to highlight the need to carry out complete POLG1 gene analysis before administration of VPA in cases of pediatric seizure disorders of unknown origin. Debut and severity of the disease in this patient was unique when compared to homozygous or heterozygous patients with the W748S mutation, leading to the conclusion that gene dosage plays a role in the clinical phenotype of this disease.

Mitochondrial disorders of DNA polymerase γ dysfunction: from anatomic to molecular pathology diagnosis

CONTEXT

Primary mitochondrial dysfunction is one of the most common causes of inherited disorders predominantly involving the neuromuscular system. Advances in the molecular study of mitochondrial DNA have changed our vision and our approach to primary mitochondrial disorders. Many of the mitochondrial disorders are caused by mutations in nuclear genes and are inherited in an autosomal recessive pattern. Among the autosomal inherited mitochondrial disorders, those related to DNA polymerase γ dysfunction are the most common and the best studied. Understanding the molecular mechanisms and being familiar with the recent advances in laboratory diagnosis of this group of mitochondrial disorders are essential for pathologists to interpret abnormal histopathology and laboratory results and to suggest further studies for a definitive diagnosis.

OBJECTIVES

To help pathologists better understand the common clinical syndromes originating from mutations in DNA polymerase γ and its associated proteins and use the stepwise approach of clinical, laboratory, and pathologic diagnosis of these syndromes.

DATA SOURCES

Review of pertinent published literature and relevant Internet databases.

CONCLUSIONS

Mitochondrial disorders are now better recognized with the development of molecular tests for clinical diagnosis. A cooperative effort among primary physicians, diagnostic pathologists, geneticists, and molecular biologists with expertise in mitochondrial disorders is required to reach a definitive diagnosis.

Mitochondrial disorders of DNA polymerase γ dysfunction: from anatomic to molecular pathology diagnosis

CONTEXT

Primary mitochondrial dysfunction is one of the most common causes of inherited disorders predominantly involving the neuromuscular system. Advances in the molecular study of mitochondrial DNA have changed our vision and our approach to primary mitochondrial disorders. Many of the mitochondrial disorders are caused by mutations in nuclear genes and are inherited in an autosomal recessive pattern. Among the autosomal inherited mitochondrial disorders, those related to DNA polymerase γ dysfunction are the most common and the best studied. Understanding the molecular mechanisms and being familiar with the recent advances in laboratory diagnosis of this group of mitochondrial disorders are essential for pathologists to interpret abnormal histopathology and laboratory results and to suggest further studies for a definitive diagnosis.

OBJECTIVES

To help pathologists better understand the common clinical syndromes originating from mutations in DNA polymerase γ and its associated proteins and use the stepwise approach of clinical, laboratory, and pathologic diagnosis of these syndromes.

DATA SOURCES

Review of pertinent published literature and relevant Internet databases.

CONCLUSIONS

Mitochondrial disorders are now better recognized with the development of molecular tests for clinical diagnosis. A cooperative effort among primary physicians, diagnostic pathologists, geneticists, and molecular biologists with expertise in mitochondrial disorders is required to reach a definitive diagnosis.

Valproic acid-associated acute liver failure in children: case report and analysis of liver transplantation outcomes in the United States

OBJECTIVE

To determine whether valproic acid (VPA)-associated acute liver failure (ALF; VPA-ALF) explains the poor outcomes after liver transplantation (LT) in children.

STUDY DESIGN

Organ Procurement and Transplantation Network data of pediatric patients who underwent LT for VPA-ALF and ALF caused by other drugs (non-VPA-drug-induced acute liver failure [DIALF]) were analyzed. Pre- and post-transplant variables and post-LT survival were compared between VPA-ALF and non-VPA-DIALF.

RESULTS

Seventeen children were transplanted for VPA-ALF. Of the 17 children, 82% died within 1 year of LT. Pre- and post-transplant parameters of VPA versus non-VPA-DIALF were comparable with two exceptions. The median alanine aminotransferase level at transplant was remarkably lower in VPA-ALF compared with non-VPA-DIALF (45 versus 1179 IU/L, P = .004). One-year survival probability was worse in VPA-ALF than non-VPA-DIALF (20% versus 69%, P < .0001). Median post-LT survival time for VPA-ALF was 2.8 months.

CONCLUSION

Children who underwent LT for VPA-ALF had a significantly lower survival probability than children with non-VPA-DIALF. Current data suggest that VPA-ALF in children represents an "unmasking" of mitochondrial disease. VPA-ALF should be a contraindication for LT, even in the absence of a documented mitochondrial disease.

A neurological perspective on mitochondrial disease

Disruption of the most fundamental cellular energy process, the mitochondrial respiratory chain, results in a diverse and variable group of multisystem disorders known collectively as mitochondrial disease. The frequent involvement of the brain, nerves, and muscles, often in the same patient, places neurologists at the forefront of the interesting and challenging process of diagnosing and caring for these patients. Mitochondrial diseases are among the most frequently inherited neurological disorders, and can be caused by mutations in mitochondrial or nuclear DNA. Substantial progress has been made over the past decade in understanding the genetic basis of these disorders, with important implications for the general neurologist in terms of the diagnosis, investigation, and multidisciplinary management of these patients.

Mitochondrial DNA depletion syndromes--many genes, common mechanisms

Mitochondrial DNA depletion syndrome has become an important cause of inherited metabolic disorders, especially in children, but also in adults. The manifestations vary from tissue-specific mtDNA depletion to wide-spread multisystemic disorders. Nine genes are known to underlie this group of disorders, and many disease genes are still unidentified. However, the disease mechanisms seem to be intimately associated with mtDNA replication and nucleotide pool regulation. We review here the current knowledge on the clinical and molecular genetic features of mitochondrial DNA depletion syndrome.

Drug management in emergent liver transplantation of mitochondrial disorder carriers: review of the literature

BACKGROUND

Mitochondrial respiratory-chain disorders (MRCD) lead to progressive disabling of neurological and cellular conditions that involve muscles, brain, kidney, and liver dysfunction. Affected individuals may need surgery, including orthotopic liver transplantation (OLT). Surgery poses anesthesia challenges because of the prolonged use of anesthetic drugs and sedatives, which may inhibit oxidative phosphorylation, mimic mitochondrial cytopathic disorders, or unveil them ex novo.

MATERIALS AND METHODS

We conducted a multilingual PubMed search of surgical and non-surgical anesthesia reports between the years 1992 and 2008, where anesthetic drugs were used in MRCD patients, especially for those undergoing urgent OLTs.

RESULTS

There were 51 case reports of 210 anesthesia and critical care interventions in patients with MRCD, a large part of them were children. Data pertaining to the safe usage of anesthesia and perioperative drugs were limited and conflicting. We found no article that addressed the issue of perioperative handling of urgent OLT in MRCD patients. We therefore suggest our own - although limited - experience for such occasions.

CONCLUSION

There are no randomized, controlled, trial-based indications regarding safe anesthetic drugs to be used perioperatively in MRCD carriers. Consultation among geneticists, anesthesiologists, intensivists, and surgeons is essential in patients with known/suspected metabolic syndrome for planning appropriate perioperative care.

Reversible valproate hepatotoxicity due to mutations in mitochondrial DNA polymerase γ (POLG1)

We report the case of a 2-year-old boy with seizures who developed hepatic failure shortly after commencing sodium valproate. Unexpectedly, liver function returned to normal on stopping the drug. Sequencing of the mitochondrial polymerase γ gene (POLG1) revealed four heterozygous substitutions, two of which have been identified in cases of Alpers-Huttenlocher disease.

POLG1Mutations Associated With Progressive Encephalopathy in Childhood

We have identified compound heterozygous missense mutations in POLG1, encoding the mitochondrial DNA polymerase gamma (Pol gamma), in 7 children with progressive encephalopathy from 5 unrelated families. The clinical features in 6 of the children included psychomotor regression, refractory seizures, stroke-like episodes, hepatopathy, and ataxia compatible with Alpers-Huttenlocher syndrome. Three families harbored a previously reported A467T substitution, which was found in compound with the earlier described G848S or the W748S substitution or a novel R574W substitution. Two families harbored the W748S change in compound with either of 2 novel mutations predicted to give an R232H or M1163R substitution. Muscle morphology showed mitochondrial myopathy with cytochrome c oxidase (COX)-deficient fibers in 4 patients. mtDNA analyses in muscle tissue revealed mtDNA depletion in 3 of the children and mtDNA deletions in the 2 sibling pairs. Neuropathologic investigation in 3 children revealed widespread cortical degeneration with gliosis and subcortical neuronal loss, especially in the thalamus, whereas there were only subcortical neurodegenerative findings in another child. The results support the concept that deletions as well as depletion of mtDNA are involved in the pathogenesis of Alpers-Huttenlocher syndrome and add 3 new POLG1 mutations associated with an early-onset neurodegenerative disease.

Mechanisms of liver injury relevant to pediatric hepatology

Hepatocyte injury and necrosis from many causes may result in pediatric liver disease. Influenced by other cell types in the liver, by its unique vascular arrangements, by lobular zonation, and by contributory effects of sepsis, reactive oxygen species and disordered hepatic architecture, the hepatocyte is prone to injury from exogenous toxins, from inborn errors of metabolism, from hepatotrophic viruses, and from immune mechanisms. Experimental studies on cultured hepatocytes or animal models must be interpreted with caution. Having discussed general concepts, this review describes immune mechanisms of liver injury, as seen in autoimmune hepatitis, hepatitis B and C infection, the anticonvulsant hypersensitivity syndrome, and autoimmune polyendocrinopathy. Of the monogenic disorders causing significant liver injury in childhood, alpha-1 antitrypsin deficiency and Niemann-Pick C disease demonstrate the effect of endoplasmic or endosomal retention of macromolecules. Tyrosinemia illustrates how understanding the biochemical defect leads to understanding cell injury, extrahepatic porphyric effects, oncogenesis, pharmacological intervention, and possible stem cell therapy. Pathogenesis of cirrhosis in galactosemia remains incompletely understood. In hereditary fructose intolerance, phosphate sequestration causes ATP depletion. Recent information about mitochondrial disease, NASH, disorders of glycosylation, Wilson's disease, and the progressive familial intrahepatic cholestases is discussed.