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Roy A, Kandettu A, Ray S, Chakrabarty S. Mitochondrial DNA replication and repair defects: Clinical phenotypes and therapeutic interventions. BIOCHIMICA ET BIOPHYSICA ACTA. BIOENERGETICS 2022; 1863:148554. [PMID: 35341749 DOI: 10.1016/j.bbabio.2022.148554] [Citation(s) in RCA: 8] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/19/2021] [Revised: 03/06/2022] [Accepted: 03/16/2022] [Indexed: 12/15/2022]
Abstract
Mitochondria is a unique cellular organelle involved in multiple cellular processes and is critical for maintaining cellular homeostasis. This semi-autonomous organelle contains its circular genome - mtDNA (mitochondrial DNA), that undergoes continuous cycles of replication and repair to maintain the mitochondrial genome integrity. The majority of the mitochondrial genes, including mitochondrial replisome and repair genes, are nuclear-encoded. Although the repair machinery of mitochondria is quite efficient, the mitochondrial genome is highly susceptible to oxidative damage and other types of exogenous and endogenous agent-induced DNA damage, due to the absence of protective histones and their proximity to the main ROS production sites. Mutations in replication and repair genes of mitochondria can result in mtDNA depletion and deletions subsequently leading to mitochondrial genome instability. The combined action of mutations and deletions can result in compromised mitochondrial genome maintenance and lead to various mitochondrial disorders. Here, we review the mechanism of mitochondrial DNA replication and repair process, key proteins involved, and their altered function in mitochondrial disorders. The focus of this review will be on the key genes of mitochondrial DNA replication and repair machinery and the clinical phenotypes associated with mutations in these genes.
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Affiliation(s)
- Abhipsa Roy
- Department of Cell and Molecular Biology, Manipal School of Life Sciences, Manipal Academy of Higher Education, Manipal 576104, Karnataka, India
| | - Amoolya Kandettu
- Department of Cell and Molecular Biology, Manipal School of Life Sciences, Manipal Academy of Higher Education, Manipal 576104, Karnataka, India
| | - Swagat Ray
- Department of Life Sciences, School of Life and Environmental Sciences, University of Lincoln, Lincoln LN6 7TS, United Kingdom
| | - Sanjiban Chakrabarty
- Department of Cell and Molecular Biology, Manipal School of Life Sciences, Manipal Academy of Higher Education, Manipal 576104, Karnataka, India.
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Li H, Wang W, Han X, Zhang Y, Dai L, Xu M, Deng J, Ding C, Wang X, Chen C, Yang X, Fang F. Clinical Attributes and Electroencephalogram Analysis of Patients With Varying Alpers' Syndrome Genotypes. Front Pharmacol 2021; 12:669516. [PMID: 34690748 PMCID: PMC8526534 DOI: 10.3389/fphar.2021.669516] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/19/2021] [Accepted: 08/30/2021] [Indexed: 11/13/2022] Open
Abstract
Alpers' syndrome is an early inceptive neurodegenerative disorder with a poor prognosis, characterized by developmental regression, intractable epilepsy, and hepatic dysfunction. Candidate genes, such as POLG, PARS2, CARS2, FARS2, NARS2, and GABRB2 are distinguished and registered following research on large cohorts that portray the clinical phenotype in such patients using expanded access to whole-exome sequencing (WES). In this study, we aimed to better understand the electroencephalogram (EEG) characteristics and clinical phenotype of different genotypes of the Alpers' syndrome, which are currently insufficiently studied. We conducted a study on seven patients with Alpers' syndrome who received treatment in Beijing Children's Hospital and had a detailed clinical EEG. Furthermore, a substantial literature search of the Chinese Biomedical Literature Database, PubMed, and Cochrane Central Register of Controlled Trials EMBASE was also conducted, which revealed a total of 22 reported cases between January 2008 to January 2021. We analyzed 29 cases of Alpers' syndrome caused by different gene variants, of which 22 cases were related to POLG gene mutation and 7 cases were related to PARS2, CARS2, FARS2, NARS2, and GABRB2 gene mutation, and found that patients with distinctive pathogenic variants exhibited comparable phenotypes and similar EEG patterns. And we defined EEG characteristics found specifically in Alpers' syndrome. Rhythmic high-amplitude delta with superimposed (poly) spikes (RHADS) is a characteristic EEG finding in the early stages of Alpers' syndrome and is a kind of epileptic phenomenon, which can provide clues for the early diagnosis of the disease.
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Affiliation(s)
- Hua Li
- Department of Neurology, Beijing Children's Hospital, Capital Medical University, National Center For Children's Health, Beijing, China
| | - Wei Wang
- Laboratory of Brain Disorders, Ministry of Science and Technology, Collaborative Innovation Center for Brain Disorders, Beijing Institute of Brain Disorders, Capital Medical University, Beijing, China.,Bioland Laboratory Guangzhou Regenerative Medicine and Health Guangdong Laboratory, Guangzhou, China
| | - Xiaodi Han
- Department of Neurology, Beijing Children's Hospital, Capital Medical University, National Center For Children's Health, Beijing, China
| | - Yujia Zhang
- Department of Neurology, Beijing Children's Hospital, Capital Medical University, National Center For Children's Health, Beijing, China
| | - Lifang Dai
- Department of Neurology, Beijing Children's Hospital, Capital Medical University, National Center For Children's Health, Beijing, China
| | - Manting Xu
- Department of Neurology, Beijing Children's Hospital, Capital Medical University, National Center For Children's Health, Beijing, China
| | - Jie Deng
- Department of Neurology, Beijing Children's Hospital, Capital Medical University, National Center For Children's Health, Beijing, China
| | - Changhong Ding
- Department of Neurology, Beijing Children's Hospital, Capital Medical University, National Center For Children's Health, Beijing, China
| | - Xiaohui Wang
- Department of Neurology, Beijing Children's Hospital, Capital Medical University, National Center For Children's Health, Beijing, China
| | - Chunhong Chen
- Department of Neurology, Beijing Children's Hospital, Capital Medical University, National Center For Children's Health, Beijing, China
| | - Xiaofeng Yang
- Bioland Laboratory Guangzhou Regenerative Medicine and Health Guangdong Laboratory, Guangzhou, China
| | - Fang Fang
- Department of Neurology, Beijing Children's Hospital, Capital Medical University, National Center For Children's Health, Beijing, China
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3
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Abstract
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.
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Levetiracetam administration is correlated with lower mortality in patients with mitochondrial encephalomyopathy, lactic acidosis, and stroke-like episodes: a retrospective study. Chin Med J (Engl) 2019; 132:269-274. [PMID: 30681492 PMCID: PMC6595817 DOI: 10.1097/cm9.0000000000000061] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022] Open
Abstract
Background: Studies on the relationship between antiepileptic drug (AED) administration and clinical outcomes in patients with mitochondrial encephalomyopathy, lactic acidosis, and stroke-like episodes (MELAS) remain scarce. Levetiracetam (LEV) is an AED that is neuroprotective in various neurologic disorders. This study aimed to determine the impact of LEV on the outcome of MELAS. Methods: A retrospective, single-center study was performed based on a large cohort of patients with MELAS with a history of seizures (n = 102). Decisions on antiepileptic therapies were made empirically. Patients were followed up for 1 to 8 years (median, 4 years) and divided into 2 groups based on whether LEV was administered (LEV or non-LEV). The modified Rankin scale (mRS) scores and mortality risks were analyzed in all patients. Results: LEV, carbamazepine, benzodiazepines, topiramate, oxcarbazepine, valproate, and lamotrigine were administered in 48, 37, 18, 13, 11, 9, and 9 patients, singly or in combination, respectively. The mean mRS score of the LEV group (n = 48) was lower than that of the non-LEV group (n = 54; mean ± standard deviation, 2.79 ± 1.47 vs. 3.83 ± 1.93, P = 0.006) up to the end of the study. Nevertheless, there was no difference in the proportion of subjects without disability (mRS ranging 0–1) between the groups (P = 0.37). The multivariate regressions revealed that LEV treatment was associated with lower mRS scores (odds ratio 0.32, 95% confidence interval [CI] 0.15–0.68, P = 0.003) and mortality rates (hazard ratio 0.24, 95% CI 0.08–0.74, P = 0.013). There was a significant difference in the Kaplan-Meier survival curves between the groups (χ2 = 4.29, P = 0.04). Conclusions: The LEV administration is associated with lower mortality in patients with MELAS in this retrospective study. Further laboratory research and prospective cohort studies are needed to confirm whether LEV has neuroprotective effects on patients with mitochondrial diseases.
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Saneto RP. An update on Alpers-Huttenlocher syndrome: pathophysiology of disease and rational treatment designs. Expert Opin Orphan Drugs 2018. [DOI: 10.1080/21678707.2018.1540979] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 10/28/2022]
Affiliation(s)
- Russell P. Saneto
- Department of Neurology, Division of Pediatric Neurology, University of Washington and Seattle Children’s Hospital, Seattle, WA, USA
- Neuroscience Institute, Center for Integrative Brain Research, Seattle Children’s Hospital, Seattle, WA, USA
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Hayhurst H, Anagnostou ME, Bogle HJ, Grady JP, Taylor RW, Bindoff LA, McFarland R, Turnbull DM, Lax NZ. Dissecting the neuronal vulnerability underpinning Alpers' syndrome: a clinical and neuropathological study. Brain Pathol 2018; 29:97-113. [PMID: 30021052 PMCID: PMC7379503 DOI: 10.1111/bpa.12640] [Citation(s) in RCA: 20] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/28/2018] [Accepted: 06/29/2018] [Indexed: 11/28/2022] Open
Abstract
Alpers’ syndrome is an early‐onset neurodegenerative disorder often caused by biallelic pathogenic variants in the gene encoding the catalytic subunit of polymerase‐gamma (POLG) which is essential for mitochondrial DNA (mtDNA) replication. Alpers’ syndrome is characterized by intractable epilepsy, developmental regression and liver failure which typically affects children aged 6 months–3 years. Although later onset variants are now recognized, they differ in that they are primarily an epileptic encephalopathy with ataxia. The disorder is progressive, without cure and inevitably leads to death from drug‐resistant status epilepticus, often with concomitant liver failure. Since our understanding of the mechanisms contributing the neurological features in Alpers’ syndrome is rudimentary, we performed a detailed and quantitative neuropathological study on 13 patients with clinically and histologically‐defined Alpers’ syndrome with ages ranging from 2 months to 18 years. Quantitative immunofluorescence showed severe respiratory chain deficiencies involving mitochondrial respiratory chain subunits of complex I and, to a lesser extent, complex IV in inhibitory interneurons and pyramidal neurons in the occipital cortex and in Purkinje cells of the cerebellum. Diminished densities of these neuronal populations were also observed. This study represents the largest cohort of post‐mortem brains from patients with clinically defined Alpers’ syndrome where we provide quantitative evidence of extensive complex I defects affecting interneurons and Purkinje cells for the first time. We believe interneuron and Purkinje cell pathology underpins the clinical development of seizures and ataxia seen in Alpers’ syndrome. This study also further highlights the extensive involvement of GABAergic neurons in mitochondrial disease.
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Affiliation(s)
- Hannah Hayhurst
- Wellcome Centre for Mitochondrial Research, Institute of Neuroscience, Newcastle University, Newcastle upon Tyne, NE2 4HH, UK
| | - Maria-Eleni Anagnostou
- Wellcome Centre for Mitochondrial Research, Institute of Neuroscience, Newcastle University, Newcastle upon Tyne, NE2 4HH, UK
| | - Helen J Bogle
- Wellcome Centre for Mitochondrial Research, Institute of Neuroscience, Newcastle University, Newcastle upon Tyne, NE2 4HH, UK
| | - John P Grady
- Wellcome Centre for Mitochondrial Research, Institute of Neuroscience, Newcastle University, Newcastle upon Tyne, NE2 4HH, UK
| | - Robert W Taylor
- Wellcome Centre for Mitochondrial Research, Institute of Neuroscience, Newcastle University, Newcastle upon Tyne, NE2 4HH, UK
| | - Laurence A Bindoff
- Department of Clinical Medicine, University of Bergen, Bergen, Norway.,Department of Neurology, Haukeland University, Bergen, Norway
| | - Robert McFarland
- Wellcome Centre for Mitochondrial Research, Institute of Neuroscience, Newcastle University, Newcastle upon Tyne, NE2 4HH, UK
| | - Doug M Turnbull
- Wellcome Centre for Mitochondrial Research, Institute of Neuroscience, Newcastle University, Newcastle upon Tyne, NE2 4HH, UK
| | - Nichola Z Lax
- Wellcome Centre for Mitochondrial Research, Institute of Neuroscience, Newcastle University, Newcastle upon Tyne, NE2 4HH, UK
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Alves CAPF, Gonçalves FG, Grieb D, Lucato LT, Goldstein AC, Zuccoli G. Neuroimaging of Mitochondrial Cytopathies. Top Magn Reson Imaging 2018; 27:219-240. [PMID: 30086109 DOI: 10.1097/rmr.0000000000000173] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/08/2023]
Abstract
Mitochondrial diseases are a complex and heterogeneous group of genetic disorders that occur as a result of either nuclear DNA or mitochondrial DNA pathogenic variants, leading to a decrease in oxidative phosphorylation and cellular energy (ATP) production. Increasing knowledge about molecular, biochemical, and genetic abnormalities related to mitochondrial dysfunction has expanded the neuroimaging phenotypes of mitochondrial disorders. As a consequence of this growing field, the imaging recognition patterns of mitochondrial cytopathies are continually evolving. In this review, we describe the main neuroimaging characteristics of pediatric mitochondrial diseases, ranging from classical to more recent and challenging features. Due to the increased knowledge about the imaging findings of mitochondrial cytopathies, the pediatric neuroradiologist plays a crucial role in the diagnosis and evaluation of these patients.
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Affiliation(s)
| | | | - Dominik Grieb
- Department of Radiology and Neuroradiology, Sana Kliniken Duisburg, Germany
| | - Leandro Tavares Lucato
- Neuroradiology Section, Hospital das Clínicas- HCFMUSP, Faculdade de Medicina, Universidade de Sao Paulo, Sao Paulo, SP, Brazil
| | - Amy C Goldstein
- Division of Human Genetics, Children's Hospital of Philadelphia, University of Pennsylvania, Philadelphia, PA
| | - Giulio Zuccoli
- Department of Radiology, University of Pittsburgh School of Medicine, Director of Pediatric Neuroradiology, Children Hospital of Pittsburgh, Pittsburgh, PA
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El-Hattab AW, Craigen WJ, Scaglia F. Mitochondrial DNA maintenance defects. Biochim Biophys Acta Mol Basis Dis 2017; 1863:1539-1555. [PMID: 28215579 DOI: 10.1016/j.bbadis.2017.02.017] [Citation(s) in RCA: 185] [Impact Index Per Article: 26.4] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/15/2016] [Revised: 01/31/2017] [Accepted: 02/14/2017] [Indexed: 01/12/2023]
Abstract
The maintenance of mitochondrial DNA (mtDNA) depends on a number of nuclear gene-encoded proteins including a battery of enzymes forming the replisome needed to synthesize mtDNA. These enzymes need to be in balanced quantities to function properly that is in part achieved by exchanging intramitochondrial contents through mitochondrial fusion. In addition, mtDNA synthesis requires a balanced supply of nucleotides that is achieved by nucleotide recycling inside the mitochondria and import from the cytosol. Mitochondrial DNA maintenance defects (MDMDs) are a group of diseases caused by pathogenic variants in the nuclear genes involved in mtDNA maintenance resulting in impaired mtDNA synthesis leading to quantitative (mtDNA depletion) and qualitative (multiple mtDNA deletions) defects in mtDNA. Defective mtDNA leads to organ dysfunction due to insufficient mtDNA-encoded protein synthesis, resulting in an inadequate energy production to meet the needs of affected organs. MDMDs are inherited as autosomal recessive or dominant traits, and are associated with a broad phenotypic spectrum ranging from mild adult-onset ophthalmoplegia to severe infantile fatal hepatic failure. To date, pathogenic variants in 20 nuclear genes known to be crucial for mtDNA maintenance have been linked to MDMDs, including genes encoding enzymes of mtDNA replication machinery (POLG, POLG2, TWNK, TFAM, RNASEH1, MGME1, and DNA2), genes encoding proteins that function in maintaining a balanced mitochondrial nucleotide pool (TK2, DGUOK, SUCLG1, SUCLA2, ABAT, RRM2B, TYMP, SLC25A4, AGK, and MPV17), and genes encoding proteins involved in mitochondrial fusion (OPA1, MFN2, and FBXL4).
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Affiliation(s)
- Ayman W El-Hattab
- Division of Clinical Genetics and Metabolic Disorders, Pediatrics Department, Tawam Hospital, Al-Ain, United Arab Emirates
| | - William J Craigen
- Department of Molecular and Human Genetics, Baylor College of Medicine, Houston, TX, USA.
| | - Fernando Scaglia
- Department of Molecular and Human Genetics, Baylor College of Medicine, Houston, TX, USA
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9
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Abstract
In the past year, several new antiepileptic drugs have emerged that have potential benefits for children with epilepsy. The spectrum of adverse effects is the principal feature that differentiates among the older drugs used to treat partial and related seizures, including simple partial, complex partial, and partial secondarily generalized seizures. Based on studies in adults with refractory seizures, the new or investigational compounds felbamate, gabapentin, lamotrigine, and vigabatrin should be active against these types of seizures in children, but none of them have been subjected to pediatric randomized controlled trials, and no studies have been done that compare new and old drugs in this category. Thus, the new drugs hold promise in children with these types of seizures, but their role relative to old drugs has not been elucidated. Several of the new drugs are active against myoclonic and generalized tonic-clonic seizures, but thus far, none have been proven to possess antiabsence activity in children. Open-label investigations suggest that lamotrigine may be helpful in Lennox-Gastaut syndrome, and vigabatrin in infantile spasms. Only felbamate has been evaluated in a randomized controlled study in children, in which it has proven beneficial against astatic and generalized tonic-clonic seizures in children with Lennox-Gastaut syndrome. Whereas investigations of these and other novel drugs are ongoing, this is an active and exciting period in pediatric antiepileptic drug development. (J Child Neurol 1994;9(Suppl):2S1-2S7).
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Affiliation(s)
- W. Edwin Dodson
- Departments of Neurology and Neurological Surgery (Neurology), and the Edward Mallinckrodt Department of Pediatrics, Washington University School of Medicine, St. Louis, MO
| | - Blaise F.D. Bourgeois
- Departments of Neurology and Neurological Surgery (Neurology), and the Edward Mallinckrodt Department of Pediatrics, Washington University School of Medicine, St. Louis, MO
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10
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Saneto RP. Alpers-Huttenlocher syndrome: the role of a multidisciplinary health care team. J Multidiscip Healthc 2016; 9:323-33. [PMID: 27555780 PMCID: PMC4968991 DOI: 10.2147/jmdh.s84900] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022] Open
Abstract
Alpers–Huttenlocher syndrome (AHS) is a mitochondrial DNA-depletion syndrome. Age of onset is bimodal: early onset at 2–4 years and later adolescent onset at 17–24 years of age. Early development is usually normal, with epilepsy heralding the disorder in ~50% of patients. The onset of seizures is coupled with progressive cognitive decline. Hepatopathy is variable, and when present is a progressive dysfunction leading to liver failure in many cases. These features of seizures, cognitive degeneration, and hepatopathy represent the “classic triad” of AHS. However, most patients develop other system involvement. Therefore, although AHS is ultimately a lethal disorder, medical care is required for sustained quality of life. Frequently, additional organ systems – gastrointestinal, respiratory, nutritional, and psychiatric – abnormalities appear and need treatment. Rarely, cardiovascular dysfunction and even pregnancy complicate medical treatment. Optimal care requires a team of physicians and caretakers to make sure quality of life is optimized. The care team, together with the family and palliative care specialists, need to be in communication as the disease progresses and medical changes occur. Although the unpredictable losses of function challenge medical care, the team approach can foster the individual quality-of-life care needed for the patient and family.
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Affiliation(s)
- Russell P Saneto
- Department of Neurology, University of Washington; Division of Pediatric Neurology, Seattle Children's Hospital, Seattle, WA, USA
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11
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Abstract
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.
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Hynynen J, Komulainen T, Tukiainen E, Nordin A, Arola J, Kälviäinen R, Jutila L, Röyttä M, Hinttala R, Majamaa K, Mäkisalo H, Uusimaa J. Acute liver failure after valproate exposure in patients with POLG1 mutations and the prognosis after liver transplantation. Liver Transpl 2014; 20:1402-12. [PMID: 25065347 DOI: 10.1002/lt.23965] [Citation(s) in RCA: 51] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/16/2014] [Revised: 07/21/2014] [Accepted: 07/21/2014] [Indexed: 01/12/2023]
Abstract
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.
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Affiliation(s)
- Johanna Hynynen
- Institute of Clinical Medicine, Department of Pediatrics, University of Oulu, Oulu, Finland; Medical Research Center, Oulu University Hospital, University of Oulu, Oulu, Finland
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13
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Luís PBM, Ruiter J, IJlst L, de Almeida IT, Duran M, Wanders RJA, Silva MFB. Valproyl-CoA inhibits the activity of ATP- and GTP-dependent succinate:CoA ligases. J Inherit Metab Dis 2014; 37:353-7. [PMID: 24154984 DOI: 10.1007/s10545-013-9657-4] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/28/2013] [Revised: 09/23/2013] [Accepted: 09/26/2013] [Indexed: 10/26/2022]
Abstract
BACKGROUND Valproic acid (VPA) is an effective antiepileptic drug that may induce progressive microvesicular steatosis. The impairment of mitochondrial function may be an important metabolic effect of VPA treatment with potential adverse consequences. OBJECTIVE To investigate the influence of VPA on the activity of GTP- and ATP-specific succinate:CoA ligases (G-SUCL and A-SUCL). METHODS The GTP- and ATP-specific SUCL activities were measured in human fibroblasts in the reverse direction, i.e. the formation of succinyl-CoA. These were assessed at different concentrations of succinate in the presence of VPA, valproyl-CoA and zinc chloride, an established inhibitor of the enzymes. Activities were measured using an optimized HPLC procedure. RESULTS Valproyl-CoA (1 mM) inhibited the activity of A-SUCL and G-SUCL by 45-55% and 25-50%, respectively. VPA (1 mM) had no influence on the activity of the two enzymes. DISCUSSION Valproyl-CoA appears to affect the activity of SUCL, especially with the ATP-specific enzyme. Considering the key role of SUCL in the Krebs cycle, interference with its activity might impair the cellular energy status. Moreover, A-SUCL is bound to the nucleoside diphosphate kinase (NDPK), which is responsible for the mitochondrial (deoxy)nucleotide synthesis. An inhibition of A-SUCL might influence the activity of NDPK inducing an imbalance of nucleotides in the mitochondria and eventually mitochondrial DNA depletion. This may account for the potential liver failure associated with valproate therapy, reported in patients with deficiencies within the mitochondrial DNA replicase system such as polymerase gamma 1.
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Affiliation(s)
- Paula B M Luís
- Research Institute for Medicines and Pharmaceutical Sciences - iMED.UL, Faculty of Pharmacy, University of Lisbon, Av. Prof. Gama Pinto, 1649-003, Lisboa, Portugal
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14
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Rahman S. Gastrointestinal and hepatic manifestations of mitochondrial disorders. J Inherit Metab Dis 2013; 36:659-73. [PMID: 23674168 DOI: 10.1007/s10545-013-9614-2] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/25/2013] [Revised: 04/13/2013] [Accepted: 04/16/2013] [Indexed: 12/23/2022]
Abstract
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.
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Affiliation(s)
- Shamima Rahman
- Mitochondrial Research Group, Clinical and Molecular Genetics Unit, UCL Institute of Child Health, 30 Guilford Street, London, WC1N 1EH, UK.
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15
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Stumpf JD, Saneto RP, Copeland WC. Clinical and molecular features of POLG-related mitochondrial disease. Cold Spring Harb Perspect Biol 2013; 5:a011395. [PMID: 23545419 DOI: 10.1101/cshperspect.a011395] [Citation(s) in RCA: 95] [Impact Index Per Article: 8.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Abstract
The inability to replicate mitochondrial genomes (mtDNA) by the mitochondrial DNA polymerase (pol γ) leads to a subset of mitochondrial diseases. Many mutations in POLG, the gene that encodes pol γ, have been associated with mitochondrial diseases such as myocerebrohepatopathy spectrum (MCHS) disorders, Alpers-Huttenlocher syndrome, myoclonic epilepsy myopathy sensory ataxia (MEMSA), ataxia neuropathy spectrum (ANS), and progressive external ophthalmoplegia (PEO). This chapter explores five important topics in POLG-related disease: (1) clinical symptoms that identify and distinguish POLG-related diseases, (2) molecular characterization of defects in polymerase activity by POLG disease variants, (3) the importance of holoenzyme formation in disease presentation, (4) the role of pol γ exonuclease activity and mutagenesis in disease and aging, and (5) novel approaches to therapy and avoidance of toxicity based on primary research in pol γ replication.
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Affiliation(s)
- Jeffrey D Stumpf
- Laboratory of Molecular Genetics, National Institute of Environmental Health Sciences, National Institutes of Health, Research Triangle Park, NC 27709, USA
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El-Hattab AW, Scaglia F. Mitochondrial DNA depletion syndromes: review and updates of genetic basis, manifestations, and therapeutic options. Neurotherapeutics 2013; 10:186-98. [PMID: 23385875 PMCID: PMC3625391 DOI: 10.1007/s13311-013-0177-6] [Citation(s) in RCA: 157] [Impact Index Per Article: 14.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/21/2023] Open
Abstract
Mitochondrial DNA (mtDNA) depletion syndromes (MDS) are a genetically and clinically heterogeneous group of autosomal recessive disorders that are characterized by a severe reduction in mtDNA content leading to impaired energy production in affected tissues and organs. MDS are due to defects in mtDNA maintenance caused by mutations in nuclear genes that function in either mitochondrial nucleotide synthesis (TK2, SUCLA2, SUCLG1, RRM2B, DGUOK, and TYMP) or mtDNA replication (POLG and C10orf2). MDS are phenotypically heterogeneous and usually classified as myopathic, encephalomyopathic, hepatocerebral or neurogastrointestinal. Myopathic MDS, caused by mutations in TK2, usually present before the age of 2 years with hypotonia and muscle weakness. Encephalomyopathic MDS, caused by mutations in SUCLA2, SUCLG1, or RRM2B, typically present during infancy with hypotonia and pronounced neurological features. Hepatocerebral MDS, caused by mutations in DGUOK, MPV17, POLG, or C10orf2, commonly have an early-onset liver dysfunction and neurological involvement. Finally, TYMP mutations have been associated with mitochondrial neurogastrointestinal encephalopathy (MNGIE) disease that typically presents before the age of 20 years with progressive gastrointestinal dysmotility and peripheral neuropathy. Overall, MDS are severe disorders with poor prognosis in the majority of affected individuals. No efficacious therapy is available for any of these disorders. Affected individuals should have a comprehensive evaluation to assess the degree of involvement of different systems. Treatment is directed mainly toward providing symptomatic management. Nutritional modulation and cofactor supplementation may be beneficial. Liver transplantation remains controversial. Finally, stem cell transplantation in MNGIE disease shows promising results.
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Affiliation(s)
- Ayman W. El-Hattab
- />Division of Medical Genetics, Department of Pediatrics, The Children’s Hospital, King Fahad Medical City and Faculty of Medicine, King Saud bin Abdulaziz University for Health Science, Riyadh, Kingdom of Saudi Arabia
| | - Fernando Scaglia
- />Department of Molecular and Human Genetics, Baylor College of Medicine, One Baylor Plaza, MS BCM225, Houston, TX 77030 USA
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Abstract
Primary mitochondrial disorders are clinically and genetically heterogeneous, caused by an alteration(s) in either mitochondrial DNA or nuclear DNA, and affect the respiratory chain's ability to undergo oxidative phosphorylation, leading to decreased production of adenosine triphosphophate and subsequent energy failure. These disorders may present at any age, but children tend to have an acute onset of disease compared with subacute or slowly progressive presentation in adults. Varying organ involvement also contributes to the phenotypic spectrum seen in these disorders. The childhood presentation of primary mitochondrial disease is mainly due to nuclear DNA mutations, with mitochondrial DNA mutations being less frequent in childhood and more prominent in adulthood disease. The clinician should be aware of the pediatric presentation of mitochondrial disease and have an understanding of the myriad of nuclear genes responsible for these disorders. The nuclear genes can be best understood by utilizing a classification system of location and function within the mitochondria.
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Affiliation(s)
- Amy C Goldstein
- Division of Child Neurology, Department of Pediatrics, Children's Hospital of Pittsburgh of UPMC, 4401 Penn Avenue, Pittsburgh, PA 15224, USA.
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18
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Abstract
Alpers-Huttenlocher syndrome is an uncommon mitochondrial disease most often associated with mutations in the mitochondrial DNA replicase, polymerase-γ. Alterations in enzyme activity result in reduced levels or deletions in mitochondrial DNA. Phenotypic manifestations occur when the functional content of mitochondrial DNA reaches a critical nadir. The tempo of disease progression and onset varies among patients, even in identical genotypes. The classic clinical triad of seizures, liver degeneration, and progressive developmental regression helps define the disorder, but a wide range of clinical expression occurs. The majority of patients are healthy before disease onset, and seizures herald the disorder in most patients. Seizures can rapidly progress to medical intractability, with frequent episodes of epilepsia partialis continua or status epilepticus. Liver involvement may precede or occur after seizure onset. Regardless, eventual liver failure is common. Both the tempo of disease progression and range of organ involvement vary from patient to patient, and are only partly explained by pathogenic effects of genetic mutations. Diagnosis involves the constellation of organ involvement, not the sequence of signs. This disorder is relentlessly progressive and ultimately fatal.
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Goldstein A, Bhatia P, Vento JM. Update on nuclear mitochondrial genes and neurologic disorders. Semin Pediatr Neurol 2012; 19:181-93. [PMID: 23245551 DOI: 10.1016/j.spen.2012.09.005] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Abstract
The majority of primary mitochondrial disorders are due to nuclear gene mutations, not aberrations within the mitochondrial genome. The nervous system is frequently involved due to its high-energy demands. Many nonspecific neurologic symptoms may be present in mitochondrial disease; however, there are well-recognized red flags that should alert the clinician to the possibility of mitochondrial disease. There is an ever increasing number of nuclear gene mutations discovered that play a role in primary mitochondrial disease and its neurologic symptomatology. Neurologists need to be aware of the wide neurologic presentation, the red-flag symptoms, and the nuclear gene mutations involved in the pathophysiology of mitochondrial disease to diagnose and manage this patient population.
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Affiliation(s)
- Amy Goldstein
- Division of Child Neurology, Department of Pediatrics, Children's Hospital of Pittsburgh of UPMC, Pittsburgh, PA 15224, USA.
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Mangalat N, Tatevian N, Bhattacharjee M, Rhoads JM. Alpers Syndrome: An Unusual Etiology of Failure to Thrive. Ultrastruct Pathol 2012; 36:219-21. [DOI: 10.3109/01913123.2012.666334] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
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21
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Finsterer J, Zarrouk Mahjoub S. Mitochondrial toxicity of antiepileptic drugs and their tolerability in mitochondrial disorders. Expert Opin Drug Metab Toxicol 2011; 8:71-9. [DOI: 10.1517/17425255.2012.644535] [Citation(s) in RCA: 80] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
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22
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Naess K, Barbaro M, Bruhn H, Wibom R, Nennesmo I, von Döbeln U, Larsson NG, Nemeth A, Lesko N. Complete Deletion of a POLG1 Allele in a Patient with Alpers Syndrome. JIMD Rep 2011; 4:67-73. [PMID: 23430898 DOI: 10.1007/8904_2011_73] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/28/2011] [Revised: 06/10/2011] [Accepted: 06/21/2011] [Indexed: 12/23/2022] Open
Abstract
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.
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Affiliation(s)
- Karin Naess
- Department of Laboratory Medicine, Division of Metabolic Diseases, Karolinska Institutet, CMMS C2-71 Karolinska University Hospital Huddinge, 141 86, Stockholm, Sweden
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Friedman SD, Shaw DWW, Ishak G, Gropman AL, Saneto RP. The use of neuroimaging in the diagnosis of mitochondrial disease. ACTA ACUST UNITED AC 2011; 16:129-35. [PMID: 20818727 DOI: 10.1002/ddrr.103] [Citation(s) in RCA: 54] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/21/2023]
Abstract
Mutations in nuclear and mitochondrial DNA impacting mitochondrial function result in disease manifestations ranging from early death to abnormalities in all major organ systems and to symptoms that can be largely confined to muscle fatigue. The definitive diagnosis of a mitochondrial disorder can be difficult to establish. When the constellation of symptoms is suggestive of mitochondrial disease, neuroimaging features may be diagnostic and suggestive, can help direct further workup, and can help to further characterize the underlying brain abnormalities. Magnetic resonance imaging changes may be nonspecific, such as atrophy (both general and involving specific structures, such as cerebellum), more suggestive of particular disorders such as focal and often bilateral lesions confined to deep brain nuclei, or clearly characteristic of a given disorder such as stroke-like lesions that do not respect vascular boundaries in mitochondrial myopathy, encephalopathy, lactic acidosis, and stroke-like episode (MELAS). White matter hyperintensities with or without associated gray matter involvement may also be observed. Across patients and discrete disease subtypes (e.g., MELAS, Leigh syndrome, etc.), patterns of these features are helpful for diagnosis. However, it is also true that marked variability in expression occurs in all mitochondrial disease subtypes, illustrative of the complexity of the disease process. The present review summarizes the role of neuroimaging in the diagnosis and characterization of patients with suspected mitochondrial disease.
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Affiliation(s)
- Seth D Friedman
- Division of Radiology, Seattle Children's Hospital/University of Washington, 4800 Sand Point Way NE, Seattle, WA 98105, USA
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24
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Abstract
The vast majority of energy necessary for cellular function is produced in mitochondria. Free-radical production and apoptosis are other critical mitochondrial functions. The complex structure, electrochemical properties of the inner mitochondrial membrane (IMM), and genetic control from both mitochondrial DNA (mtDNA) and nuclear DNA (nDNA) are some of the unique features that explain why the mitochondria are vulnerable to environmental injury. Because of similarity to bacterial translational machinery, mtDNA translation is likewise vulnerable to inhibition by some antibiotics. The mechanism of mtDNA replication, which is required for normal mitochondrial maintenance and duplication, is inhibited by a relatively new class of drugs used to treat AIDS. The electrochemical gradient maintained by the IMM is vulnerable to many drugs that are weak organic acids at physiological pH, resulting in excessive free-radical generation and uncoupling of oxidative phosphorylation. Many of these drugs can cause clinical injury in otherwise healthy people, but there are also examples where particular gene mutations may predispose to increased drug toxicity. The spectrum of drug-induced mitochondrial dysfunction extends across many drug classes. It is hoped that preclinical pharmacogenetic and functional studies of mitochondrial toxicity, along with personalized genomic medicine, will improve both our understanding of mitochondrial drug toxicity and patient safety.
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Affiliation(s)
- Bruce H Cohen
- Cleveland Clinic Lerner College of Medicine, Case Western Reserve University, 9500 Euclid Avenue, Cleveland, OH 44195, USA.
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25
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Saneto RP, Naviaux RK. Polymerase gamma disease through the ages. ACTA ACUST UNITED AC 2010; 16:163-74. [DOI: 10.1002/ddrr.105] [Citation(s) in RCA: 65] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/15/2023]
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26
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The clinical diagnosis of POLG disease and other mitochondrial DNA depletion disorders. Methods 2010; 51:364-73. [DOI: 10.1016/j.ymeth.2010.05.008] [Citation(s) in RCA: 87] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/24/2010] [Accepted: 05/25/2010] [Indexed: 01/06/2023] Open
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Saneto RP, Lee IC, Koenig MK, Bao X, Weng SW, Naviaux RK, Wong LJC. POLG DNA testing as an emerging standard of care before instituting valproic acid therapy for pediatric seizure disorders. Seizure 2010; 19:140-6. [PMID: 20138553 DOI: 10.1016/j.seizure.2010.01.002] [Citation(s) in RCA: 93] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/28/2009] [Revised: 12/31/2009] [Accepted: 01/07/2010] [Indexed: 11/17/2022] Open
Abstract
PURPOSE To review our clinical experience and determine if there are appropriate signs and symptoms to consider POLG sequencing prior to valproic acid (VPA) dosing in patients with seizures. METHODS Four patients who developed VPA-induced hepatotoxicity were examined for POLG sequence variations. A subsequent chart review was used to describe clinical course prior to and after VPA dosing. RESULTS Four patients of multiple different ethnicities, age 3-18 years, developed VPA-induced hepatotoxicity. All were given VPA due to intractable partial seizures. Three of the patients had developed epilepsia partialis continua. The time from VPA exposure to liver failure was between 2 and 3 months. Liver failure was reversible in one patient. Molecular studies revealed homozygous p.R597W or p.A467T mutations in two patients. The other two patients showed compound heterozygous mutations, p.A467T/p.Q68X and p.L83P/p.G888S. Clinical findings and POLG mutations were diagnostic of Alpers-Huttenlocher syndrome. CONCLUSION Our cases underscore several important findings: POLG mutations have been observed in every ethnic group studied to date; early predominance of epileptiform discharges over the occipital region is common in POLG-induced epilepsy; the EEG and MRI findings varying between patients and stages of the disease; and VPA dosing at any stage of Alpers-Huttenlocher syndrome can precipitate liver failure. Our data support an emerging proposal that POLG gene testing should be considered in any child or adolescent who presents or develops intractable seizures with or without status epilepticus or epilepsia partialis continua, particularly when there is a history of psychomotor regression.
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Affiliation(s)
- Russell P Saneto
- Division of Pediatric Neurology, Seattle Children's Hospital/University of Washington, Seattle, WA 98105, USA
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28
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Wolf NI, Rahman S, Schmitt B, Taanman JW, Duncan AJ, Harting I, Wohlrab G, Ebinger F, Rating D, Bast T. Status epilepticus in children with Alpers’ disease caused byPOLG1mutations: EEG and MRI features. Epilepsia 2009; 50:1596-607. [DOI: 10.1111/j.1528-1167.2008.01877.x] [Citation(s) in RCA: 112] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
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29
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Oldfors A, Tulinius M. Mitochondrial encephalomyopathies. HANDBOOK OF CLINICAL NEUROLOGY 2007; 86:125-165. [PMID: 18808998 DOI: 10.1016/s0072-9752(07)86006-4] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/26/2023]
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30
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Kakinuma H, Fujiki T, Nakamura T, Takahashi H. Valproate hepatotoxicity in a 5-year-old boy with cerebral palsy due to neonatal asphyxia. Pediatr Int 2006; 48:631-3. [PMID: 17168987 DOI: 10.1111/j.1442-200x.2006.02267.x] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Hiroaki Kakinuma
- Department of Pediatrics, Kanazawa Medical University, Ishikawa, Japan.
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31
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Abstract
Therapy for mitochondrial diseases is woefully inadequate. However, lack of a cure does not equate with lack of treatment. Palliative therapy is dictated by good medical practice and includes anticonvulsant medication, control of endocrine dysfunction, and surgical procedures. Removal of noxious metabolites is centered on combating lactic acidosis, but extends to other metabolites. Attempts to bypass blocks in the respiratory chain by administration of electron acceptors have not been successful, but this may be amenable to genetic engineering. Administration of metabolites and cofactors is the mainstay of real-life therapy and is especially important in disorders due to primary deficiencies of specific compounds, such as carnitine or coenzyme Q10 (CoQ10). There is increasing interest in the administration of reactive oxygen radicals (ROS) scavengers, both in primary mitochondrial diseases and in neurodegenerative diseases. Gene therapy is a challenge because of polyplasmy and heteroplasmy, but novel experimental approaches are being pursued. One important strategy is to decrease the ratio of mutant to wild-type mitochondrial genomes ("gene shifting") by different means: (1) converting mutated mitochondrial DNA (mtDNA) genes into normal nuclear DNA genes ("allotopic expression"); (2) importing cognate genes from other species ("xenotopic expression"); (3) correcting mtDNA mutations by importing specific restriction endonucleases; (4) selecting for respiratory function; and (5) inducing muscle regeneration. Germline therapy raises ethical problems but is being considered for prevention of maternal transmission of mtDNA mutations. Preventive therapy through genetic counseling and prenatal diagnosis is becoming increasingly important for nuclear DNA-related disorders.
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Affiliation(s)
- Salvatore DiMauro
- Department of Neurology, Columbia University Medical Center, 4-420 College of Physicians and Surgeons, 630 West 168th Street, New York, New York 10032, USA.
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32
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Davidzon G, Mancuso M, Ferraris S, Quinzii C, Hirano M, Peters HL, Kirby D, Thorburn DR, DiMauro S. POLG mutations and Alpers syndrome. Ann Neurol 2005; 57:921-3. [PMID: 15929042 DOI: 10.1002/ana.20498] [Citation(s) in RCA: 95] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Abstract
Alpers-Huttenlocher syndrome (AHS) an autosomal recessive hepatocerebral syndrome of early onset, has been associated with mitochondrial DNA (mtDNA) depletion and mutations in polymerase gamma gene (POLG). We have identified POLG mutations in four patients with hepatocerebral syndrome and mtDNA depletion in liver, who fulfilled criteria for AHS. All were compound heterozygous for the G848S and W748S mutations, previously reported in patients with progressive external ophtalmoplegia or ataxia. We conclude that AHS should be included in the clinical spectrum of mtDNA depletion and is often associated with POLG mutations, which can cause either multiple mtDNA deletions or mtDNA depletion.
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Affiliation(s)
- Guido Davidzon
- Department of Neurology, Columbia University College of Physicians and Surgeons, New York, NY 10032, USA
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33
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Simonati A, Filosto M, Savio C, Tomelleri G, Tonin P, Dalla Bernardina B, Rizzuto N. Features of cell death in brain and liver, the target tissues of progressive neuronal degeneration of childhood with liver disease (Alpers-Huttenlocher disease). Acta Neuropathol 2003; 106:57-65. [PMID: 12721699 DOI: 10.1007/s00401-003-0698-x] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/28/2002] [Revised: 02/17/2003] [Accepted: 02/17/2003] [Indexed: 11/30/2022]
Abstract
Alpers-Huttenlocher disease (AHD) is a rare encephalopathy of infancy and childhood characterized by myoclonic seizures and progressive neurological deterioration, usually associated with signs and symptoms of liver dysfunction. There is no biological marker of the disease, and ultimate diagnosis still relies on pathological examination. Features of clinical progression and pathological findings suggest AHD to be secondary to a genetically determined disorder of mitochondrial function. We report on four AHD patients and focus on their pathological features in brain, liver and muscle. Liver and muscle biopsy specimens were examined using histochemical markers of the oxidative pathways, probes to immunodetect molecules of the apoptotic cascades and electron microscopy. In liver (but not in muscle) biopsy samples, activated caspases were detected by immunohistochemistry: foci of caspase-9-positive cells were seen in a child affected with chronic, progressive fibrosis. In an 18-year-old boy, who suffered from valproic acid-associated acute hepatitis, caspase-3 cells were clustered among the necrotic foci and the foamy cells. In both patients electron microscopy revealed apoptotic nuclei. Normal muscle biopsy specimens were observed in two children, 2 and 8 years-old respectively; in the 18-year-old patient cytochrome oxidase-negative fibers as well as ultrastructural findings of mitochondrial abnormalities were observed. In no patient was there biochemical evidence of impaired oxidative metabolism. Neuropathological examination of the brains of two patients (13 months and 19 years old, respectively) showed focal distribution of the lesions affecting the telencephalic cortex and, to a lesser extent, subcortical gray nuclei. Along with the necrotizing lesions, characterized by neuronal loss, neuropil microcysts and newly formed vessels, we also observed acutely shrunken neurons and features of apoptotic cell death in the cerebral cortex only. Severe neuronal loss without necrotizing features was observed in the cerebellar cortex. The presence of both anoxic and apoptotic nuclei in brain and liver, the target tissues of the disease, is consistent with the hypothesis that abnormal activation of mitochondrion-related cell death pathways might be involved in the pathogenesis of AHD.
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Affiliation(s)
- Alessandro Simonati
- Department of Neurological and Visual Sciences, Section of Neurology, Policlinico GB Rossi, University of Verona, P.le LA Scuro 1, 37134 Verona, Italy.
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Abstract
Valproic acid (VPA) is an effective anticonvulsant useful in many types of epilepsy and, although it is usually well tolerated, it has been associated with many neurological and systemic side effects. Among these, one of the most important is VPA-induced hyperammonemic encephalopathy (VHE): its typical signs are acute onset of impaired consciousness, focal neurologic symptoms, and increased seizure frequency. The pathogenesis of VHE is still unclear, but it has been suggested that hyperammonemia can produce encephalopathy via inhibition of glutamate uptake by astrocytes which may lead to potential neuronal injury and perhaps cerebral edema. Glutamine production is increased, whereas its release is inhibited in astrocytes exposed to ammonia. The elevated glutamine increases intracellular osmolarity, promoting an influx of water with resultant astrocytic swelling. This swelling could compromise astrocyte energy metabolism and result in cerebral edema with increased intracranial pressure. Moreover, VHE seems to be more frequently in patients with carnitine deficiency or with congenital urea cycle enzymatic defects.
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Abstract
Pharmacokinetic differences may play a part in the age-related differences in the incidence of adverse effects. The most common idiosyncratic reaction to lamotrigine (LTG) is rash, affecting 10-20% of patients. Risk factors are young age, concurrent valproate (VPA), high starting dose, and rapid escalation. In children, cytochrome P450 (CYP)-catalyzed metabolism is increased, and uridine diphosphate (UDP)-glucuronosyltransferase (UGT)-catalyzed metabolism is not significantly different from that in adults. A CYP-catalyzed arene oxide intermediate of LTG has been identified. The increase CYP metabolism of LTG in children could result in increased formation of the reactive metabolite and a higher incident of rash. Children often received higher milligram per kilogram doses compared with adults. The higher dose would cause an increased amount of LTG metabolized to the reactive arene oxide intermediate. VPA therapy is associated with a transient elevation in liver-function tests in 15-30% of patients and a rare, fatal hepatotoxicity. Most cases of VPA hepatotoxicity occurred in children younger than 2 years who had preexisting neurologic or other physical defects. Hypotheses regarding the pathogenesis of the hepatotoxicity include preexisting mitochondrial disease or inborn errors of metabolism, VPA inhibition of beta-oxidation, and toxicity from VPA metabolites VPA, 4-ene-VPA, and 2,4-diene-VPA. Infants and children have higher concentration ratios of 4-ene-VPA to VPA. Polytherapy with enzyme inducers increases the formation of the hepatotoxic metabolites. The role of underlying metabolic disorders associated with hepatodegeneration and intractable seizures without VPA is a major confounder in identifying risk factors and demonstrates the difficulty in separating underlying disease factors in rare idiosyncratic reactions.
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Affiliation(s)
- Gail D Anderson
- Department of Pharmacy, University of Washington, Seattle 98195, USA.
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36
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Kayihan N, Nennesmo I, Ericzon BG, Németh A. Fatal deterioration of neurological disease after orthotopic liver transplantation for valproic acid-induced liver damage. Pediatr Transplant 2000; 4:211-4. [PMID: 10933322 DOI: 10.1034/j.1399-3046.2000.00115.x] [Citation(s) in RCA: 34] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
Abstract
We describe a 12-year-old girl with an early onset neurologic disease of slow progressiveness and electro-encephalography showing epileptic activity. The girl developed fulminant liver failure 5 months after the start of valproic acid treatment. Repeated mitochondrial assays failed to prove a mitochondrial disorder, but muscle biopsies were slightly pathological. Liver histology indicated acute-on-chronic liver disease. Six weeks after a successful orthotopic liver transplantation her neurological condition deteriorated rapidly, soon leading to generalized cortical disease and death. Post-mortem brain examination showed advanced central nervous destruction. We suggest that this is a late-onset Huttenlocher variant of Alpers' syndrome, where fulminant liver failure can be triggered by valproic acid, and orthotopic liver transplantation can subsequently trigger a fatal neurologic deterioration. Our case illustrates that when a referral center receives a previously unknown patient with hepatocellular insufficiency, it might be impossible to differentiate between fulminant vs. acute-on-chronic liver failure, and the decision whether to perform a liver transplantation or not would become difficult.
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Affiliation(s)
- N Kayihan
- Department of Pediatrics, Karolinska Institutet, Huddinge University Hospital, Sweden
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37
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38
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Rasmussen M, Sanengen T, Skullerud K, Kvittingen EA, Skjeldal OH. Evidence that Alpers-Huttenlocher syndrome could be a mitochondrial disease. J Child Neurol 2000; 15:473-7. [PMID: 10921519 DOI: 10.1177/088307380001500709] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
Abstract
We report an 11-year-old boy with a slight developmental delay and epilepsy. After he was placed on valproate, he developed hepatic failure and increasing neurologic symptoms, including epilepsia partialis continua, and died. Autopsy findings in liver and cerebrum were consistent with progressive neuronal degeneration of childhood with liver disease, also called Alpers-Huttenlocher syndrome. Ragged red fibers and cytochrome c oxidase negative fibers were present in muscle. These results suggest that Alpers-Huttenlocher syndrome, at least in some patients, is a mitochondrial disease.
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Affiliation(s)
- M Rasmussen
- Department of Pediatrics, National Hospital, Oslo, Norway
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39
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Abstract
Japanese encephalitis (JE) is the commonest endemic encephalitis but there are very few studies on the radiological changes and these are based on relatively small number of patients. The present study aims at comparing the CT scan and MRI findings in JE and correlate these with the reported histopathological findings. Forty two patients with JE were subjected to detailed neurological examination. Cranial CT scan was carried out in 38 and MRI scan in 31 patients. Haemagglutination inhibition test was carried out in the acute and convalescent sera. The CT scan and MRI findings have been compared. Both CT scan and MRI were available in 28 patients. In 21 patients, CT scans were abnormal and changes included thalamic hypodensity in 15, midbrain and basal ganglia hypodensity in 1 patient each, cerebral oedema in 4 and cortical atrophy with ventricular dilatation in 2 patients. MRI however was abnormal in all 31 patients including 17 with normal CT scan. Cranial MRI revealed either mixed intensity or hypointense lesion on T(1) and hyperintense or mixed intensity lesion on T(2) in thalami in all except two patients. The MRI lesions were also noted in basal ganglia in 11, midbrain in 18, pons in 8, cerebellum and cerebral cortex in 6 patients each and subcortical white matter in 2 patients. MRI was more sensitive than CT scan in revealing thalamic and extrathalamic abnormalities. Thalamic changes may be helpful in the diagnosis of JE especially in endemic area.
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Affiliation(s)
- J Kalita
- Department of Neurology, Sanjay Gandhi PGIMS, Lucknow, India
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40
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Delarue A, Paut O, Guys JM, Montfort MF, Lethel V, Roquelaure B, Pellissier JF, Sarles J, Camboulives J. Inappropriate liver transplantation in a child with Alpers-Huttenlocher syndrome misdiagnosed as valproate-induced acute liver failure. Pediatr Transplant 2000; 4:67-71. [PMID: 10731063 DOI: 10.1034/j.1399-3046.2000.00090.x] [Citation(s) in RCA: 54] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
Abstract
A 3-yr-old boy received valproic acid (VPA) for recurrent seizures. He developed coma and acute liver failure that were attributed to VPA toxicity, and underwent emergency orthotopic liver transplantation (OLTx). Despite good graft function, his neurological state worsened and led to death a few months later. The diagnosis of Alpers-Huttenlocher Syndrome (AHS) was suspected, subsequently to liver Tx, in view of ongoing neurologic deterioration and magnetic resonance imaging (MRI) findings. The syndrome, recessively inherited, associates brain degeneration with liver failure, and is now considered a mitochondrial disease. Enzyme activity deficiencies of the respiratory chain were identified in muscle mitochondria, as well as morphologic abnormalities of mitochondria in the explanted liver. Guidelines for diagnosis are presented, in order to differentiate the liver failure in AHS from that induced by genuine VPA toxicity. It is recommended to avoid liver Tx in patients with AHS given the fatal neurological course of the disease.
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Affiliation(s)
- A Delarue
- Department of Pediatric Surgery, Hôpital Timone-Enfants, Marseille, France
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41
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Thomson MA, Lynch S, Strong R, Shepherd RW, Marsh W. Orthotopic liver transplantation with poor neurologic outcome in valproate-associated liver failure: a need for critical risk-benefit appraisal in the use of valproate. Transplant Proc 2000; 32:200-3. [PMID: 10701024 DOI: 10.1016/s0041-1345(99)00936-7] [Citation(s) in RCA: 22] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
Affiliation(s)
- M A Thomson
- Queensland Liver Transplant Service, Royal Children's Hospital, Brisbane, Australia
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Abstract
Mitochondrial respiratory chain disorders are an established cause of liver failure in early childhood but they are probably under-diagnosed, partly due to under-recognition and partly due to the difficulty of investigation. It is particularly important to look for mitochondrial disorders if the liver disease presents with hypoglycaemia and lactic acidaemia or if it is accompanied by neurological, muscle or renal tubular abnormalities. Respiratory chain defects have been demonstrated in a number of patients who die of liver failure following severe epilepsy; this includes at least some cases of Alpers syndrome or 'progressive neuronal degeneration of childhood'. In mitochondrial liver disease, histology usually shows steatosis, often accompanied by fibrosis, cholestasis and loss of hepatocytes. Unless the clinical picture suggests a particular syndrome, such as Pearson syndrome, biochemical assays and histochemistry should be the initial investigations. Ideally, investigations should be carried out on liver as well as more standard tissues, such as muscle, since defects can be tissue-specific. Nuclear defects and mtDNA point mutations are probably responsible for many cases of mitochondrial liver disease but, as yet, the only identified molecular abnormalities are mtDNA rearrangements and mtDNA depletion. Treatment of mitochondrial liver disease is unsatisfactory. If the disease is confined to the liver, transplantation may be appropriate but in several patients transplantation has been followed by the appearance of disease in other organs, particularly the brain.
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Affiliation(s)
- A A Morris
- Department of Child Health, University of Newcastle Upon Tyne, Royal Victoria Infirmary, Newcastle, UK
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Affiliation(s)
- A Baker
- Department of Paediatric Liver, King's College Hospital, London, UK
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44
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Poley JR, Nowicki MJ. Other hereditary diseases and the liver. BAILLIERE'S CLINICAL GASTROENTEROLOGY 1998; 12:369-407. [PMID: 9890078 DOI: 10.1016/s0950-3528(98)90140-3] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
In this chapter, an abbreviated account is presented on the subject of hereditary diseases and the liver. However, it is incomplete because Alagille syndrome, storage disorders, alpha-1-antitrypsin deficiency and Wilson disease are not included as they appear in other chapters of this volume. Biliary atresia is omitted because all available evidence does not support any significant genetic association. Molecular biological techniques have enabled linkage of several liver cholestatic disorders to chromosomal loci, and further characterization of the canalicular bile salt transporter (cBST) will advance our understanding of pathogenetic mechanisms involved in benign and progressive cholestatic syndromes. Disorders that have been treated as separate entities may have common 'roots', exemplified by the concept of the ductal plate malformation in fibropolycystic disease. Whereas the majority of disorders referred to in this chapter present early in life, there are several that are associated with liver failure in the neonatal period, which makes early recognition particularly important. Liver transplantation offers a cure for many hereditary disorders affecting the liver but it is not applicable to all.
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Affiliation(s)
- J R Poley
- Department of Paediatrics, Children's Hospital of The King's Daughters, Norfolk, Virginia, USA
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Abstract
Metabolic disorders are a relatively uncommon, but important, cause of childhood seizures. Routinely searching for a metabolic disorder in epilepsy is usually unrewarding. Children and adolescents with epilepsy can be selected for appropriate biochemical investigation by considering the seizure type, age of onset, EEG appearance, family history, clinical findings and the results of brain imaging. A limited number of biochemical screening tests can be used to categorize the more common metabolic disorders associated with seizures.
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Affiliation(s)
- J Gibbs
- Department of Paediatrics, Countess of Chester Hospital, UK
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Schwabe MJ, Dobyns WB, Burke B, Armstrong DL. Valproate-induced liver failure in one of two siblings with Alpers disease. Pediatr Neurol 1997; 16:337-43. [PMID: 9258971 DOI: 10.1016/s0887-8994(97)00030-1] [Citation(s) in RCA: 33] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Abstract
Alpers disease is a neurodegenerative disorder of childhood characterized by early developmental delay, intractable seizures, and death in childhood. Neuropathologic changes are most severe in the gray matter and consist of diffuse neuronal loss, spongiform changes, and astrocytosis. We report 2 siblings with Alpers disease who were discordant for exposure to valproate (VPA). Both had developmental delay, and a progressive seizure disorder beginning at 5 years of age. The proband died at age 8 years of complications of ongoing seizures, including epilepsia partialis continua, with only minimal liver abnormalities. Her younger brother was treated with VPA for new-onset seizures and developed fulminant liver failure 6 months later, which led to his death at 5 years of age. Neuropathologic abnormalities of both siblings were consistent with Alpers disease. These observations support classification of Alpers disease and Alpers disease with liver cirrhosis as a single disease. They also confirm previous reports indicating that VPA may accelerate fulminant liver failure in Alpers disease. We recommend that a diagnosis of Alpers disease be considered in children with unexplained early developmental delay, cerebellar signs, or partial seizures, especially epilepsia partialis continua. When Alpers disease is strongly suspected, use of VPA should be avoided.
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Affiliation(s)
- M J Schwabe
- Department of Pediatrics, University of Minnesota Medical School, Minneapolis, USA
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Morris AA, Singh-Kler R, Perry RH, Griffiths PD, Burt AD, Wong CP, Gardner-Medwin D, Turnbull DM. Respiratory chain dysfunction in progressive neuronal degeneration of childhood with liver disease. J Child Neurol 1996; 11:417-9. [PMID: 8877614 DOI: 10.1177/088307389601100517] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/02/2023]
Affiliation(s)
- A A Morris
- Medical School, Department of Paediatric Neurology, Newcastle General Hospital, Newcastle Upon Tyne, England
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Fromenty B, Pessayre D. Inhibition of mitochondrial beta-oxidation as a mechanism of hepatotoxicity. Pharmacol Ther 1995; 67:101-54. [PMID: 7494860 DOI: 10.1016/0163-7258(95)00012-6] [Citation(s) in RCA: 445] [Impact Index Per Article: 15.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
Severe and prolonged impairment of mitochondrial beta-oxidation leads to microvesicular steatosis, and, in severe forms, to liver failure, coma and death. Impairment of mitochondrial beta-oxidation may be either genetic or acquired, and different causes may add their effects to inhibit beta-oxidation severely and trigger the syndrome. Drugs and some endogenous compounds can sequester coenzyme A and/or inhibit mitochondrial beta-oxidation enzymes (aspirin, valproic acid, tetracyclines, several 2-arylpropionate anti-inflammatory drugs, amineptine and tianeptine); they may inhibit both mitochondrial beta-oxidation and oxidative phosphorylation (endogenous bile acids, amiodarone, perhexiline and diethylaminoethoxyhexestrol), or they may impair mitochondrial DNA transcription (interferon-alpha), or decrease mitochondrial DNA replication (dideoxynucleoside analogues), while other compounds (ethanol, female sex hormones) act through a combination of different mechanisms. Any investigational molecule should be screened for such effects.
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Affiliation(s)
- B Fromenty
- Institut National de la Santé et de la Recherche Médicale Unité 24, Hôpital Beaujon, Clichy, France
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49
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Abstract
L-Carnitine supplementation has been recommended to prevent the fatal hepatotoxic effects associated with valproic acid. We report on a child with fatal valproate-related hepatotoxic effects despite this supplementation.
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Affiliation(s)
- J V Murphy
- Neurology Section, Children's Mercy Hospital, Kansas City, Missouri 64108
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50
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Millichap JG. Hepatocerebral Degeneration or Valproate Toxicity. Pediatr Neurol Briefs 1993. [DOI: 10.15844/pedneurbriefs-7-1-12] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022] Open
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