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Feng Z, Lai R, Wei J, Liu X, Chen X, Liu Y, Qin W, Qin X, Kong F. Have one's view of the important overshadowed by the trivial: chronic progressive external ophthalmoplegia combined with unilateral facial nerve injury: a case report and literature review. Front Neurol 2024; 14:1268053. [PMID: 38249737 PMCID: PMC10797034 DOI: 10.3389/fneur.2023.1268053] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/27/2023] [Accepted: 12/05/2023] [Indexed: 01/23/2024] Open
Abstract
Chronic progressive external ophthalmoplegia (CPEO) is a mitochondrial encephalomyopathy that is characterized by progressive ptosis and impaired ocular motility. Owing to its nonspecific clinical manifestations, CPEO is often misdiagnosed as other conditions. Herein, we present the case of a 34-year-old woman who primarily presented with incomplete left eyelid closure and limited bilateral eye movements. During the 6-year disease course, she was diagnosed with myasthenia gravis and cranial polyneuritis. Finally, skeletal muscle tissue biopsy confirmed the diagnosis. Biopsy revealed pathological changes in mitochondrial myopathy. Furthermore, mitochondrial gene testing of the skeletal muscle revealed a single chrmM:8469-13447 deletion. In addition, we summarized the findings of 26 patients with CPEO/Kearns-Sayre syndrome who were misdiagnosed with other diseases owing to ocular symptoms. In conclusion, we reported a rare clinical case and emphasized the symptomatic diversity of CPEO. Furthermore, we provided a brief review of the diagnosis and differential diagnosis of the disease.
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Affiliation(s)
- Ziyang Feng
- The Fourth Clinical Medical College, Guangzhou University of Chinese Medicine, Shenzhen, China
| | - Rui Lai
- School of Acupuncture and Tuina, Chengdu University of Traditional Chinese Medicine, Chengdu, China
| | - Jia Wei
- The Fourth Clinical Medical College, Guangzhou University of Chinese Medicine, Shenzhen, China
- Department of Encephalopathy and Psychology, Shenzhen Traditional Chinese Medicine Hospital, Shenzhen, China
| | - Xuan Liu
- The Fourth Clinical Medical College, Guangzhou University of Chinese Medicine, Shenzhen, China
- Department of Encephalopathy and Psychology, Shenzhen Traditional Chinese Medicine Hospital, Shenzhen, China
| | - Xueqin Chen
- The Fourth Clinical Medical College, Guangzhou University of Chinese Medicine, Shenzhen, China
- Department of Encephalopathy and Psychology, Shenzhen Traditional Chinese Medicine Hospital, Shenzhen, China
| | - Yangsicheng Liu
- The Fourth Clinical Medical College, Guangzhou University of Chinese Medicine, Shenzhen, China
| | - Wenxin Qin
- The Fourth Clinical Medical College, Guangzhou University of Chinese Medicine, Shenzhen, China
| | - Xiude Qin
- The Fourth Clinical Medical College, Guangzhou University of Chinese Medicine, Shenzhen, China
- Department of Encephalopathy and Psychology, Shenzhen Traditional Chinese Medicine Hospital, Shenzhen, China
| | - Fanxin Kong
- The Fourth Clinical Medical College, Guangzhou University of Chinese Medicine, Shenzhen, China
- Department of Encephalopathy and Psychology, Shenzhen Traditional Chinese Medicine Hospital, Shenzhen, China
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2
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Aldendail CF, Caress JB. Bilateral Hypertrophic Olivary Degeneration in a syndrome of Sensory Ataxic Neuropathy with Dysarthria and Ophthalmoplegia. Muscle Nerve 2022; 66:E15-E18. [PMID: 35906095 DOI: 10.1002/mus.27689] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/13/2022] [Revised: 07/26/2022] [Accepted: 07/26/2022] [Indexed: 11/12/2022]
Affiliation(s)
- Carolyn F Aldendail
- Wake Forest University School of Medicine, Department of Neurology, Atrium Health Wake Forest Baptist, Department of Neurology, 1 Medical Center Blvd., Winston-Salem, NC
| | - James B Caress
- Wake Forest University School of Medicine, Department of Neurology, Atrium Health Wake Forest Baptist, Department of Neurology, 1 Medical Center Blvd., Winston-Salem, NC
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3
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Novel biallelic mutations in POLG gene: large deletion and missense variant associated with PEO. Neurol Sci 2021; 42:4271-4280. [PMID: 34189666 DOI: 10.1007/s10072-021-05380-2] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/06/2021] [Accepted: 06/03/2021] [Indexed: 10/21/2022]
Abstract
BACKGROUND Mitochondrial disorders are clinically heterogeneous diseases associated with impaired oxidative phosphorylation (OXPHOS) activity. POLG, which encodes the DNA polymerase-γ (Polγ) catalytic subunit, is the most commonly mutated nuclear gene associated with mitochondrial disorders. METHODS We carried out whole-exome sequencing (WES) to identify the gene associated with progressive external ophthalmoplegia (PEO). We then performed histopathological analyses, assessed mitochondrial biology, and executed functional studies to evaluate the potential pathogenicity of the identified genetic mutations. RESULTS Novel biallelic POLG mutations, including a large deletion mutation (exons 7-21) and a missense variant c.1796C>T (p.Thr599Ile) were detected in the proband. Histopathological analysis of a biopsied muscle sample from this patient revealed the presence of approximately 20% COX-negative fibers. Bioinformatics analyses confirmed that the detected mutations were pathogenic. Furthermore, levels of mitochondrial complex I, II, and IV subunit protein expressions were found to be decreased in the proband, and marked impairment of mitochondrial respiration was evident in cells harboring these mutations. CONCLUSION This study expands the spectrum of known POLG variants associated with PEO and advances current understanding regarding the structural and functional impacts of these mutations.
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4
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Nicolau S, Milone M, Liewluck T. Guidelines for genetic testing of muscle and neuromuscular junction disorders. Muscle Nerve 2021; 64:255-269. [PMID: 34133031 DOI: 10.1002/mus.27337] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/28/2021] [Accepted: 05/28/2021] [Indexed: 12/24/2022]
Abstract
Despite recent advances in the understanding of inherited muscle and neuromuscular junction diseases, as well as the advent of a wide range of genetic tests, patients continue to face delays in diagnosis of sometimes treatable disorders. These guidelines outline an approach to genetic testing in such disorders. Initially, a patient's phenotype is evaluated to identify myopathies requiring directed testing, including myotonic dystrophies, facioscapulohumeral muscular dystrophy, oculopharyngeal muscular dystrophy, mitochondrial myopathies, dystrophinopathies, and oculopharyngodistal myopathy. Initial investigation in the remaining patients is generally a comprehensive gene panel by next-generation sequencing. Broad panels have a higher diagnostic yield and can be cost-effective. Due to extensive phenotypic overlap and treatment implications, genes responsible for congenital myasthenic syndromes should be included when evaluating myopathy patients. For patients whose initial genetic testing is negative or inconclusive, phenotypic re-evaluation is warranted, along with consideration of genes and variants not included initially, as well as their acquired mimickers.
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Affiliation(s)
- Stefan Nicolau
- Department of Neurology, Mayo Clinic, Rochester, Minnesota, USA
| | | | - Teerin Liewluck
- Department of Neurology, Mayo Clinic, Rochester, Minnesota, USA
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5
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Belyakova-Bodina A, Ratanov M, Schneider E, Seliverstov Y, Nuzhnyi E, Klyushnikov S, Broutian A. Uncovering bilateral vestibulopathy in patients with SANDO syndrome caused by mutations in POLG gene: a case series. J Neurol 2021; 268:3909-3912. [PMID: 34117923 DOI: 10.1007/s00415-021-10650-2] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/25/2021] [Revised: 06/03/2021] [Accepted: 06/04/2021] [Indexed: 11/30/2022]
Affiliation(s)
| | | | - Erich Schneider
- Institute of Medical Technology, Brandenburg University of Technology Cottbus, Senftenberg, Germany
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Li LX, Jiang LT, Pan YG, Zhang XL, Pan LZ, Nie ZY, Chen YH, Jin LJ. Clinical and Molecular Features of POLG-Related Sensory Ataxic Neuropathy with Dysarthria and Ophthalmoparesis. J Mol Neurosci 2021; 71:2462-2467. [PMID: 33791913 DOI: 10.1007/s12031-021-01831-9] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/25/2020] [Accepted: 03/15/2021] [Indexed: 10/21/2022]
Abstract
Sensory ataxic neuropathy, dysarthria, and ophthalmoparesis (SANDO) is a rare mitochondrial disorder associated with mutations in the POLG gene, which encodes the DNA polymerase gamma catalytic subunit. A few POLG-related SANDO cases have been reported, but the genotype-phenotype correlation remains unclear. Here, we report a patient with SANDO carrying two novel missense variants (c.2543G>C, p.G848A and c.452 T>C, p.L151P) in POLG. We also reviewed previously reported cases to systematically evaluate the clinical and genetic features of POLG-related SANDO. A total of 35 distinct variants in the coding region of POLG were identified in 63 patients with SANDO. The most frequent variant was the p.A467T variant, followed by the p.W748S variant. The clinical spectrum of SANDO is heterogeneous. No clear correlation has been observed between the mutation types and clinical phenotypes. Our findings expand the mutational spectrum of POLG and contribute to clinical management and genetic counseling for POLG-related SANDO.
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Affiliation(s)
- Li-Xi Li
- Neurotoxin Research Center of Key Laboratory of Spine and Spinal Cord Injury Repair and Regeneration of Ministry of Education, Neurological Department of Tongji Hospital, Tongji University School of Medicine, Shanghai, China
| | - Li-Ting Jiang
- Neurotoxin Research Center of Key Laboratory of Spine and Spinal Cord Injury Repair and Regeneration of Ministry of Education, Neurological Department of Tongji Hospital, Tongji University School of Medicine, Shanghai, China
| | - You-Gui Pan
- Neurotoxin Research Center of Key Laboratory of Spine and Spinal Cord Injury Repair and Regeneration of Ministry of Education, Neurological Department of Tongji Hospital, Tongji University School of Medicine, Shanghai, China
| | - Xiao-Long Zhang
- Neurotoxin Research Center of Key Laboratory of Spine and Spinal Cord Injury Repair and Regeneration of Ministry of Education, Neurological Department of Tongji Hospital, Tongji University School of Medicine, Shanghai, China
| | - Li-Zhen Pan
- Neurotoxin Research Center of Key Laboratory of Spine and Spinal Cord Injury Repair and Regeneration of Ministry of Education, Neurological Department of Tongji Hospital, Tongji University School of Medicine, Shanghai, China
| | - Zhi-Yu Nie
- Neurotoxin Research Center of Key Laboratory of Spine and Spinal Cord Injury Repair and Regeneration of Ministry of Education, Neurological Department of Tongji Hospital, Tongji University School of Medicine, Shanghai, China
| | - Yu-Hui Chen
- Neurotoxin Research Center of Key Laboratory of Spine and Spinal Cord Injury Repair and Regeneration of Ministry of Education, Neurological Department of Tongji Hospital, Tongji University School of Medicine, Shanghai, China
| | - Ling-Jing Jin
- Neurotoxin Research Center of Key Laboratory of Spine and Spinal Cord Injury Repair and Regeneration of Ministry of Education, Neurological Department of Tongji Hospital, Tongji University School of Medicine, Shanghai, China.
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7
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Patient-specific neural progenitor cells derived from induced pluripotent stem cells offer a promise of good models for mitochondrial disease. Cell Tissue Res 2020; 380:15-30. [PMID: 31925525 DOI: 10.1007/s00441-019-03164-x] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/04/2019] [Accepted: 12/19/2019] [Indexed: 02/06/2023]
Abstract
Mitochondria are the primary generators of ATP in eukaryotic cells through the process of oxidative phosphorylation. Mitochondria are also involved in several other important cellular functions including regulation of intracellular Ca2+, cell signaling and apoptosis. Mitochondrial dysfunction causes disease and since it is not possible to perform repeated studies in humans, models are essential to enable us to investigate the mechanisms involved. Recently, the discovery of induced pluripotent stem cells (iPSCs), made by reprogramming adult somatic cells (Takahashi and Yamanaka 2006; Yamanaka and Blau 2010), has provided a unique opportunity for studying aspects of disease mechanisms in patient-specific cells and tissues. Reprogramming cells to neuronal lineage such as neural progenitor cells (NPCs) generated from the neural induction of reprogrammed iPSCs can thus provide a useful model for investigating neurological disease mechanisms including those caused by mitochondrial dysfunction. In addition, NPCs display a huge clinical potential in drug screening and therapeutics.
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8
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Hypertrophic olivary degeneration: A comprehensive review focusing on etiology. Brain Res 2019; 1718:53-63. [DOI: 10.1016/j.brainres.2019.04.024] [Citation(s) in RCA: 19] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/13/2019] [Revised: 04/08/2019] [Accepted: 04/22/2019] [Indexed: 12/27/2022]
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9
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Meira B, Roque R, Pinto M, Caetano A. Late-onset presentation of POLG1-associated mitochondrial disease. BMJ Case Rep 2019; 12:12/3/e228482. [PMID: 30936349 DOI: 10.1136/bcr-2018-228482] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/03/2022] Open
Abstract
Mutations in the nuclear POLG1 gene compromise the integrity of mitochondrial DNA and show great allelic and clinical heterogeneity. Among adult POLG1-associated mitochondrial disease, the main clinical feature is chronic progressive external ophthalmoplegia. Other related clinical manifestations are sensory or cerebellar ataxia, peripheral neuropathy, myopathy or extrapyramidal symptoms. We report the case of a 72-year-old man who presented with a late onset sensory neuronopathy, chronic progressive external ophthalmoplegia, gait ataxia and parkinsonism. Genetic studies showed a compound heterozygosity of known pathogenic mutations in the POLG1 gene (variant T252I/P587 L in cis configuration in allele 1 and variant R807C in allele 2). Late life presentation highlights that mitochondrial disorders should be considered regardless of age of onset of symptoms.
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Affiliation(s)
- Bruna Meira
- Neurology Department, Centro Hospitalar de Lisboa Ocidental EPE, Lisboa, Portugal
| | - Rafael Roque
- Neuropathology Unit - Neurology Department, Centro Hospitalar Lisboa Norte EPE, Lisboa, Portugal
| | - Miguel Pinto
- Neurology Department, Centro Hospitalar de Lisboa Ocidental EPE, Lisboa, Portugal
| | - André Caetano
- Neurology Department, Centro Hospitalar de Lisboa Ocidental EPE, Lisboa, Portugal
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Bilateral Vestibulopathy Aggravates Balance and Gait Disturbances in Sensory Ataxic Neuropathy, Dysarthria, and Ophthalmoparesis: A Case Report. J Clin Neuromuscul Dis 2017; 18:34-6. [PMID: 27552387 DOI: 10.1097/cnd.0000000000000126] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
In patients with a triad of sensory ataxic neuropathy, dysarthria, and ophthalmoparesis (SANDO), the presenting features are mainly ataxia or ptosis. SANDO patients often have impaired balance and gait, which is not surprising considering the combination of sensory ataxic neuropathy, and additional symptoms like cerebellar ataxia and limb girdle weakness. We describe a SANDO patient who noticed an increasingly impaired balance and gait, without any dizziness. Neurological investigation revealed an external ophthalmeplegia and a cerebellar ataxia; the head impulse test was not reliable because of eye movement disorders. The caloric reflex tests showed lack of responses on both sides, compatible with severe bilateral vestibulopathy. Making the diagnosis of bilateral vestibulopathy in SANDO patients may have implications for the management of the patient, because specific vestibular rehabilitation can improve gaze and postural stability.
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11
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Henao AI, Pira S, Herrera DA, Vargas SA, Montoya J, Castillo M. Characteristic brain MRI findings in ataxia-neuropathy spectrum related to POLG mutation. Neuroradiol J 2016; 29:46-8. [PMID: 26755490 DOI: 10.1177/1971400915621324] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022] Open
Abstract
Patients with mutations in the polymerase gamma gene (POLG) may present with progressive ataxia and in such situations neuroimaging findings may suggest the diagnosis. Herein we report a patient with a POLG gene W748S homozygous mutation and characteristic lesions in the thalamus, cerebellum and inferior olivary nucleus seen on magnetic resonance imaging.
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Affiliation(s)
- Adriana I Henao
- Department of Pediatric Neurology, Universidad de Antioquia, Medellín, Colombia
| | - Sonia Pira
- Department of Pediatric Neurology, Universidad de Antioquia, Medellín, Colombia
| | - Diego A Herrera
- Department of Radiology, Universidad de Antioquia, Medellín, Colombia Department of Radiology, CediMed (Centro Avanzado de Diagnóstico Médico), Medellín, Colombia
| | - Sergio A Vargas
- Department of Radiology, Universidad de Antioquia, Medellín, Colombia Department of Radiology, CediMed (Centro Avanzado de Diagnóstico Médico), Medellín, Colombia
| | - Jorge Montoya
- Department of Genetics, Universidad de Antioquia, Medellín, Colombia
| | - Mauricio Castillo
- Department of Radiology, University of North Carolina, Chapel Hill, NC, USA
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12
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Novel POLG mutation in a patient with sensory ataxia, neuropathy, ophthalmoparesis and stroke. Clin Chim Acta 2015; 448:211-4. [DOI: 10.1016/j.cca.2015.06.028] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/08/2015] [Revised: 06/22/2015] [Accepted: 06/22/2015] [Indexed: 02/04/2023]
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13
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Hanisch F, Kornhuber M, Alston CL, Taylor RW, Deschauer M, Zierz S. SANDO syndrome in a cohort of 107 patients with CPEO and mitochondrial DNA deletions. J Neurol Neurosurg Psychiatry 2015; 86:630-4. [PMID: 25143630 DOI: 10.1136/jnnp-2013-306748] [Citation(s) in RCA: 37] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/17/2013] [Accepted: 07/23/2014] [Indexed: 11/04/2022]
Abstract
OBJECTIVE The sensory ataxic neuropathy with dysarthria and ophthalmoparesis (SANDO) syndrome is a subgroup of mitochondrial chronic progressive external ophthalmoplegia (CPEO)-plus disorders associated with multiple mitochondrial DNA (mtDNA) deletions. There is no systematic survey on SANDO in patients with CPEO with either single or multiple large-scale mtDNA deletions. METHODS In this retrospective analysis, we characterised the frequency, the genetic and clinical phenotype of 107 index patients with mitochondrial CPEO (n=66 patients with single and n=41 patients with multiple mtDNA deletions) and assessed these for clinical evidence of a SANDO phenotype. Patients with multiple mtDNA deletions were additionally screened for mutations in the nuclear-encoded POLG, SLC25A4, PEO1 and RRM2B genes. The clinical, histological and genetic data of 11 patients with SANDO were further analysed. RESULTS None of the 66 patients with single, large-scale mtDNA deletions fulfilled the clinical criteria of SANDO syndrome. In contrast, 9 of 41 patients (22%) with multiple mtDNA deletions and two additional family members fulfilled the clinical criteria for SANDO. Within this subgroup, multiple mtDNA deletions were associated with the following nuclear mutations: POLG (n=6), PEO1 (n=2), unidentified (n=2). The combination of sensory ataxic neuropathy with ophthalmoparesis (SANO) was observed in 70% of patients with multiple mtDNA deletions but only in 4% with single deletions. The combination of CPEO and sensory ataxic neuropathy (SANO, incomplete SANDO) was found in 43% of patients with multiple mtDNA deletions but not in patients with single deletions. CONCLUSION The SANDO syndrome seems to indicate a cluster of symptoms within the wide range of multisystemic symptoms associated with mitochondrial CPEO. SANO seems to be the most frequent phenotype associated with multiple mtDNA deletions in our cohort but not or is rarely associated with single, large-scale mtDNA deletions.
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Affiliation(s)
- Frank Hanisch
- Department of Neurology, Martin-Luther-University Halle-Wittenberg, Halle (Saale), Germany
| | - Malte Kornhuber
- Department of Neurology, Martin-Luther-University Halle-Wittenberg, Halle (Saale), Germany
| | - Charlotte L Alston
- Wellcome Trust Centre for Mitochondrial Research, The Medical School, Framlington Place, Newcastle University, Newcastle upon Tyne, UK
| | - Robert W Taylor
- Wellcome Trust Centre for Mitochondrial Research, The Medical School, Framlington Place, Newcastle University, Newcastle upon Tyne, UK
| | - Marcus Deschauer
- Department of Neurology, Martin-Luther-University Halle-Wittenberg, Halle (Saale), Germany
| | - Stephan Zierz
- Department of Neurology, Martin-Luther-University Halle-Wittenberg, Halle (Saale), Germany
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14
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Mukai M, Sugaya K, Matsubara S, Cai H, Yabe I, Sasaki H, Nakano I. [Familial progressive external opthalmoplegia, parkinsonism and polyneuropathy associated with POLG1 mutation]. Rinsho Shinkeigaku 2015; 54:417-22. [PMID: 24943079 DOI: 10.5692/clinicalneurol.54.417] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022]
Abstract
Multiple mitochondrial DNA (mtDNA) deletions usually occur secondarily to a mutation in one of the enzymes involved in mtDNA maintenance, such as polymerase γ, which is encoded by the nuclear polymerase γ1 gene (POLG1) and POLG2. Patients with multiple mtDNA deletion disorders show clinical heterogeneity of symptoms, in addition to usually seen progressive external ophthalmoplegia (PEO). We conducted clinical, histological and genetic analyses of two affected sisters in a family with the autosomal dominant inheritance pattern of PEO. A 73-year-old woman (patient 1) with congenital hypogonadism and PEO developed L-dopa responsive parkinsonism about the age of 60. Neurological examination revealed mild proximal muscle weakness and polyneuropathy too. Her 69-year-old sister (patient 2) also showed PEO, parkinsonism and polyneuropathy. Histopathological studies of biopsied muscle specimens from patient 1 revealed numerous ragged red fibers as well as fibers with increased succinate dehydrogenase activity and decreased cytochrome c oxidase activity. Multiple mtDNA deletions were detected, both by Southern blot and long-range PCR assays of total DNA from the biopsied muscle specimens. A systemic mutational analysis in both sisters revealed a heterozygous p.Y955C (c.2864A>G) mutation in POLG1. This is the first Japanese family identified with this mutation. We reviewed cases with this mutation highlighting a wide phenotypic spectrum of this disorder.
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Affiliation(s)
- Masako Mukai
- Department of Neurology, Tokyo Metropolitan Neurological Hospital
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15
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Zierz CM, Joshi PR, Zierz S. Frequencies of myohistological mitochondrial changes in patients with mitochondrial DNA deletions and the common m.3243A>G point mutation. Neuropathology 2014; 35:130-6. [DOI: 10.1111/neup.12173] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/15/2014] [Accepted: 09/10/2014] [Indexed: 11/27/2022]
Affiliation(s)
- Charlotte Maria Zierz
- Department of Neurology; Martin-Luther-University, Halle-Wittenberg; Halle/Saale Germany
| | - Pushpa Raj Joshi
- Department of Neurology; Martin-Luther-University, Halle-Wittenberg; Halle/Saale Germany
| | - Stephan Zierz
- Department of Neurology; Martin-Luther-University, Halle-Wittenberg; Halle/Saale Germany
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16
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Beh SC, Frohman TC, Frohman EM. Neuro-ophthalmic Manifestations of Cerebellar Disease. Neurol Clin 2014; 32:1009-80. [DOI: 10.1016/j.ncl.2014.07.002] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
Affiliation(s)
- Shin C Beh
- Department of Neurology, University of Texas Southwestern Medical Center, 5323 Harry Hines Boulevard, Dallas, TX 75390, USA
| | - Teresa C Frohman
- Department of Neurology, University of Texas Southwestern Medical Center, 5323 Harry Hines Boulevard, Dallas, TX 75390, USA
| | - Elliot M Frohman
- Department of Neurology, University of Texas Southwestern Medical Center, 5323 Harry Hines Boulevard, Dallas, TX 75390, USA; Department of Ophthalmology, University of Texas Southwestern Medical Center, 5323 Harry Hines Boulevard, Dallas, TX 75390, USA.
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17
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Prasun P. Rare variant of unknown significance in POLG1 and diagnostic dilemma. J Neurol 2014; 261:2218-20. [DOI: 10.1007/s00415-014-7493-6] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/18/2014] [Revised: 09/03/2014] [Accepted: 09/04/2014] [Indexed: 01/03/2023]
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18
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Matilla-Dueñas A, Ashizawa T, Brice A, Magri S, McFarland KN, Pandolfo M, Pulst SM, Riess O, Rubinsztein DC, Schmidt J, Schmidt T, Scoles DR, Stevanin G, Taroni F, Underwood BR, Sánchez I. Consensus paper: pathological mechanisms underlying neurodegeneration in spinocerebellar ataxias. CEREBELLUM (LONDON, ENGLAND) 2014; 13:269-302. [PMID: 24307138 PMCID: PMC3943639 DOI: 10.1007/s12311-013-0539-y] [Citation(s) in RCA: 97] [Impact Index Per Article: 9.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
Intensive scientific research devoted in the recent years to understand the molecular mechanisms or neurodegeneration in spinocerebellar ataxias (SCAs) are identifying new pathways and targets providing new insights and a better understanding of the molecular pathogenesis in these diseases. In this consensus manuscript, the authors discuss their current views on the identified molecular processes causing or modulating the neurodegenerative phenotype in spinocerebellar ataxias with the common opinion of translating the new knowledge acquired into candidate targets for therapy. The following topics are discussed: transcription dysregulation, protein aggregation, autophagy, ion channels, the role of mitochondria, RNA toxicity, modulators of neurodegeneration and current therapeutic approaches. Overall point of consensus includes the common vision of neurodegeneration in SCAs as a multifactorial, progressive and reversible process, at least in early stages. Specific points of consensus include the role of the dysregulation of protein folding, transcription, bioenergetics, calcium handling and eventual cell death with apoptotic features of neurons during SCA disease progression. Unresolved questions include how the dysregulation of these pathways triggers the onset of symptoms and mediates disease progression since this understanding may allow effective treatments of SCAs within the window of reversibility to prevent early neuronal damage. Common opinions also include the need for clinical detection of early neuronal dysfunction, for more basic research to decipher the early neurodegenerative process in SCAs in order to give rise to new concepts for treatment strategies and for the translation of the results to preclinical studies and, thereafter, in clinical practice.
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Affiliation(s)
- A Matilla-Dueñas
- Health Sciences Research Institute Germans Trias i Pujol (IGTP), Ctra. de Can Ruti, Camí de les Escoles s/n, Badalona, Barcelona, Spain,
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Tanaka K, Tateishi T, Kawamura N, Ohyagi Y, Urata M, Kira JI. [A case of sensory ataxic neuropathy, dysarthria, and ophthalmoparesis with multiple mitochondrial DNA deletions]. Rinsho Shinkeigaku 2014; 53:205-11. [PMID: 23524600 DOI: 10.5692/clinicalneurol.53.205] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022]
Abstract
We report the case of a 62-year-old man with sensory ataxic neuropathy, dysarthria, and ophthalmoparesis (SANDO). He developed gait disturbance at 54 years of age, muscle weakness at 56 years, and difficulty hearing at 58 years. His brother had muscle weakness in both legs from age 20 years, and was diagnosed with Charcot-Marie-Tooth disease because he had muscle weakness of the four extremities, decreased CMAP and SNAP amplitudes on peripheral nerve conduction tests, and loss of large myelinated fibers and onion-bulb formations on sural nerve biopsy. His brother died aged 46 years, but no accurate cause of death was identified. Neurological examination of the present patient revealed bilateral ptosis, external ophthalmoparesis, dysarthria, dysphagia, sensorineural hearing loss, mild weakness and atrophy of proximal muscles in all four limbs, severe sensory ataxia, and disturbance of deep sensation in his legs. He showed elevation of lactate and pyruvate levels in cerebrospinal fluid and serum. An aerobic exercise test disclosed a marked increase in lactate and pyruvate levels in serum. On nerve conduction study, amplitudes of CMAP and SNAP, and F wave-evoked frequency were decreased. Needle electromyography showed chronic neurogenic patterns with fibrillation potentials in the extremity muscles. Head MRI demonstrated T2 prolonged lesions in the bilateral basal ganglia, while brain MRS revealed a small lactate peak. Biopsy of his left lateral vastus muscle showed ragged-red fibers and group atrophy, and some muscle fibers had decreased cytochrome c activity. Left sural nerve biopsy revealed a marked loss of large myelinated fibers, and some onion-bulb formations. Genetic testing disclosed a large mtDNA deletion in the biopsied muscle. Among nuclear genes, we found point mutations in ANT-1 (exon 1 c.105G>A, 5' untranslated region) and POLG-1 (exon 4, c.1218G>A, p. and exon 23 c.3920C>T, p.A1217V). We diagnosed SANDO. This is the first case of SANDO with large mitochondrial DNA deletions in Japanese.
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Affiliation(s)
- Koji Tanaka
- Department of Neurology, Neurological Institute, Graduate School of Medical Sciences, Kyushu University
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Tang S, Wang J, Zhang VW, Li FY, Landsverk M, Cui H, Truong CK, Wang G, Chen LC, Graham B, Scaglia F, Schmitt ES, Craigen WJ, Wong LJC. Transition to next generation analysis of the whole mitochondrial genome: a summary of molecular defects. Hum Mutat 2013; 34:882-93. [PMID: 23463613 DOI: 10.1002/humu.22307] [Citation(s) in RCA: 68] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/13/2012] [Accepted: 02/15/2013] [Indexed: 01/06/2023]
Abstract
The diagnosis of mitochondrial disorders is challenging because of the clinical variability and genetic heterogeneity. Conventional analysis of the mitochondrial genome often starts with a screening panel for common mitochondrial DNA (mtDNA) point mutations and large deletions (mtScreen). If negative, it has been traditionally followed by Sanger sequencing of the entire mitochondrial genome (mtWGS). The recently developed "Next-Generation Sequencing" (NGS) technology offers a robust high-throughput platform for comprehensive mtDNA analysis. Here, we summarize the results of the past 6 years of clinical practice using the mtScreen and mtWGS tests on 9,261 and 2,851 unrelated patients, respectively. A total of 344 patients (3.7%) had mutations identified by mtScreen and 99 (3.5%) had mtDNA mutations identified by mtWGS. The combinatorial analyses of mtDNA and POLG revealed a diagnostic yield of 6.7% in patients with suspected mitochondrial disorders but no recognizable syndromes. From the initial mtWGS-NGS cohort of 391 patients, 21 mutation-positive cases (5.4%) have been identified. The mtWGS-NGS provides a one-step approach to detect common and uncommon point mutations, as well as deletions. Additionally, NGS provides accurate, sensitive heteroplasmy measurement, and the ability to map deletion breakpoints. A new era of more efficient molecular diagnosis of mtDNA mutations has arrived.
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Affiliation(s)
- Sha Tang
- Department of Molecular and Human Genetics, Baylor College of Medicine, Houston, Texas 77030, USA
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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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Wong LJC. Challenges of bringing next generation sequencing technologies to clinical molecular diagnostic laboratories. Neurotherapeutics 2013; 10:262-72. [PMID: 23269496 PMCID: PMC3625389 DOI: 10.1007/s13311-012-0170-5] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/13/2023] Open
Abstract
Molecular diagnosis of complex dual genome mitochondrial disorders is a challenge. It requires the identification of deleterious mutations in one of the ~1,500 nuclear genes and the mitochondrial genome. If the molecular defect is in the mitochondrial genome, quantification of degree of mutation load (heteroplasmy) in affected tissues is important. Due to the extreme clinical and genetic heterogeneity, conventional sequence analysis of the candidate genes one-by-one is impractical, if not impossible. The newly developed massively parallel next generation sequencing (NGS) technique, that allows simultaneous sequence analysis of multiple target genes, when appropriately validated with deep coverage and proper quality controls, can be used as an effective comprehensive diagnostic approach in CLIA certified clinical laboratories.
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Affiliation(s)
- Lee-Jun C Wong
- Department of Molecular and Human Genetics, Baylor College of Medicine, One Baylor Plaza, NAB 2015, Houston, TX 77030, USA.
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Early-onset ataxia with progressive external ophthalmoplegia associated with POLG mutation: autosomal recessive mitochondrial ataxic syndrome or SANDO? Neurologist 2013; 18:287-9. [PMID: 22931735 DOI: 10.1097/nrl.0b013e318266f5a6] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Abstract
Autosomal recessive ataxias caused by mutations of the polymerase γ (POLG) gene make an important group of progressive ataxias accompanied by a diverse spectrum of neurological disorders. Because the clinical picture can be quite miscellaneous, it is challenging to assort patients to any of the currently described syndromes; therefore, to provide such a patient with a conclusive diagnosis can be challenging for the neurologist. A typical magnetic resonance imaging finding is probably the most useful landmark in the diagnostic process, which will steer the clinician toward POLG gene testing. To illustrate this, we present a case of progressive ataxia caused by A467T and W748S mutations of POLG gene, who presented with overlapping symptoms of autosomal recessive mitochondrial ataxic syndrome and SANDO, as well as choreoathetotic movements and dysphonia. After lengthy investigations, magnetic resonance imaging showed T2 and FLAIR hyperintensities in the thalamus, inferior olives, and cerebellum, which led us to the analysis of POLG mutations.
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Comprehensive next-generation sequence analyses of the entire mitochondrial genome reveal new insights into the molecular diagnosis of mitochondrial DNA disorders. Genet Med 2013; 15:388-94. [PMID: 23288206 DOI: 10.1038/gim.2012.144] [Citation(s) in RCA: 86] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/21/2023] Open
Abstract
PURPOSE The application of massively parallel sequencing technology to the analysis of the mitochondrial genome has demonstrated great improvement in the molecular diagnosis of mitochondrial DNA-related disorders. The objective of this study was to investigate the performance characteristics and to gain new insights into the analysis of the mitochondrial genome. METHODS The entire mitochondrial genome was analyzed as a single amplicon using a long-range PCR-based enrichment approach coupled with massively parallel sequencing. The interference of the nuclear mitochondrial DNA homologs was distinguished from the actual mitochondrial DNA sequences by comparison with the results obtained from conventional PCR-based Sanger sequencing using multiple pairs of primers. RESULTS Our results demonstrated the uniform coverage of the entire mitochondrial genome. Massively parallel sequencing of the single amplicon revealed the presence of single-nucleotide polymorphisms and nuclear homologs of mtDNA sequences that cause the erroneous and inaccurate variant calls when PCR/Sanger sequencing approach was used. This single amplicon massively parallel sequencing strategy provides an accurate quantification of mutation heteroplasmy as well as the detection and mapping of mitochondrial DNA deletions. CONCLUSION The ability to quantitatively and qualitatively evaluate every single base of the entire mitochondrial genome is indispensible to the accurate molecular diagnosis and genetic counseling of mitochondrial DNA-related disorders. This new approach may be considered as first-line testing for comprehensive analysis of the mitochondrial genome.Genet Med 2013:15(5):388-394.
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Abstract
Inborn errors of metabolism may impact on muscle and peripheral nerve. Abnormalities involve mitochondria and other subcellular organelles such as peroxisomes and lysosomes related to the turnover and recycling of cellular compartments. Treatable causes are β-oxidation defects producing progressive neuropathy; pyruvate dehydrogenase deficiency, porphyria, or vitamin B12 deficiency causing recurrent episodes of neuropathy or acute motor deficit mimicking Guillain-Barré syndrome. On the other hand, lysosomal (mucopolysaccharidosis, Gaucher and Fabry diseases), mitochondriopathic (mitochondrial or nuclear mutations or mDNA depletion), peroxisomal (adrenomyeloneuropathy, Refsum disease, sterol carrier protein-2 deficiency, cerebrotendinous xanthomatosis, α-methylacyl racemase deficiency) diseases are multisystemic disorders involving also the heart, liver, brain, retina, and kidney. Pathophysiology of most metabolic myopathies is related to the impairment of energy production or to abnormal production of reactive oxygen species (ROS). Main symptoms are exercise intolerance with myalgias, cramps and recurrent myoglobinuria or limb weakness associated with elevation of serum creatine kinase. Carnitine palmitoyl transferase deficiency, followed by acid maltase deficiency, and lipin deficiency, are the most common cause of isolated rhabdomyolysis. Metabolic myopathies are frequently associated to extra-neuromuscular disorders particularly involving the heart, liver, brain, retina, skin, and kidney.
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Affiliation(s)
- Adele D'Amico
- Molecular Medicine and Unit of Neuromuscular and Neurodegenerative Diseases, IRCCS-Children's Hospital Bambino Gesù, Rome, Italy
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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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Kinghorn KJ, Kaliakatsos M, Blakely EL, Taylor RW, Rich P, Clarke A, Omer S. Hypertrophic olivary degeneration on magnetic resonance imaging in mitochondrial syndromes associated with POLG and SURF1 mutations. J Neurol 2012; 260:3-9. [PMID: 22729384 DOI: 10.1007/s00415-012-6564-9] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/27/2012] [Accepted: 05/18/2012] [Indexed: 11/26/2022]
Abstract
Hypertrophic olivary degeneration (HOD) is associated with lesions within the dento-rubro-olivary pathway or Guillain-Mollaret triangle and may be associated clinically with palatal tremor. Here we report HOD on brain magnetic resonance (MR) imaging in three patients with progressive mitochondrial syndromes in the absence of palatal tremor. Two of the patients were found to have identical compound heterozygous mutations in the POLG gene, encoding the catalytic subunit of the mitochondrial DNA polymerase-γ, but presented with different clinical phenotypes. The first patient displayed the clinical syndrome of sensory ataxia, neuropathy, dysarthria, and ophthalmoparesis (SANDO), while the second patient was affected by a neurological disorder consisting of an ophthalmoplegia, myopathy, and neuropathy. The third case was a child with Leigh syndrome due to SURF1 gene mutations, who presented with a generalized tremor. We discuss the brain MR imaging findings in these three cases along with a literature review on the MR features of previously reported cases of patients with POLG gene mutations and Leigh disease due to SURF1 gene mutations. Our findings suggest that the presence of HOD, in the appropriate clinical setting, should alert the clinician to the possibility of a mitochondrial disorder and the need to screen for mutations in POLG and SURF1 genes.
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Affiliation(s)
- K J Kinghorn
- Department of Neurology, St. George's Hospital, London, UK
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McKelvie P, Marotta R, Thorburn DR, Chin J, Punchihewa S, Collins S. A case of myelopathy, myopathy, peripheral neuropathy and subcortical grey matter degeneration associated with recessive compound heterozygous POLG1 mutations. Neuromuscul Disord 2012; 22:401-5. [PMID: 22357363 DOI: 10.1016/j.nmd.2011.10.017] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/21/2011] [Revised: 10/06/2011] [Accepted: 10/26/2011] [Indexed: 11/18/2022]
Abstract
This 54year old woman presented with symptoms of sensory ataxic neuropathy, with cerebellar features. She developed further weakness, visual disturbances with diplopia, dysarthria and dysphasia. After her death at 66years, she was found to have compound heterozygous mutations of POLG1 gene in muscle, and Southern blot showed low levels of multiple deletions of mitochondrial DNA. Neuropathological examination showed profound dorsal column and dorsal spinocerebellar tract degeneration, degeneration of dorsal root ganglia and Clarke's nucleus in spinal cord and severe predominantly sensory peripheral neuropathy. The brain showed severe neuronal loss and gliosis in substantia nigra, medial posterior thalamus and head of caudate. Excess numbers of COX-negative fibres and "ragged-red" fibres were found in five skeletal muscles sampled.
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Affiliation(s)
- P McKelvie
- Department of Anatomical Pathology, St. Vincent's Hospital Melbourne, Australia.
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Finsterer J. Inherited Mitochondrial Disorders. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2012; 942:187-213. [DOI: 10.1007/978-94-007-2869-1_8] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
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Mitochondrial neurogastrointestinal encephalomyopathy (MNGIE)-like phenotype: an expanded clinical spectrum of POLG1 mutations. J Neurol 2011; 259:862-8. [PMID: 21993618 DOI: 10.1007/s00415-011-6268-6] [Citation(s) in RCA: 45] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/26/2011] [Revised: 09/23/2011] [Accepted: 09/26/2011] [Indexed: 12/22/2022]
Abstract
The aim of the study was to determine the prevalence of MNGIE-like phenotype in patients with recessive POLG1 mutations. Mutations in the POLG1 gene, which encodes for the catalytic subunit of the mitochondrial DNA polymerase gamma essential for mitochondrial DNA replication, cause a wide spectrum of mitochondrial disorders. Common phenotypes associated with POLG1 mutations include Alpers syndrome, ataxia-neuropathy syndrome, and progressive external ophthalmoplegia (PEO). Mitochondrial neurogastrointestinal encephalomyopathy (MNGIE) is an autosomal recessive disorder characterized by severe gastrointestinal dysmotility, cachexia, PEO and/or ptosis, peripheral neuropathy, and leukoencephalopathy. MNGIE is caused by TYMP mutations. Rare cases of MNGIE-like phenotype have been linked to RRM2B mutations. Recently, POLG1 mutations were identified in a family with clinical features of MNGIE but no leukoencephalopathy. The coding regions and exon-intron boundaries of POLG1 were sequence analyzed in patients suspected of POLG1 related disorders. Clinical features of 92 unrelated patients with two pathogenic POLG1 alleles were carefully reviewed. Three patients, accounting for 3.3% of all patients with two pathogenic POLG1 mutations, were found to have clinical features consistent with MNGIE but no leukoencephalopathy. Patient 1 carries p.W748S and p.R953C; patient 2 is homozygous for p.W748S, and patient 3 is homozygous for p.A467T. In addition, patient 2 has a similarly affected sibling with the same POLG1 genotype. POLG1 mutations may cause MNGIE-like syndrome, but the lack of leukoencephalopathy and the normal plasma thymidine favor POLG1 mutations as responsible molecular defect.
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Schaaf CP, Blazo M, Lewis RA, Tonini RE, Takei H, Wang J, Wong LJ, Scaglia F. Early-onset severe neuromuscular phenotype associated with compound heterozygosity for OPA1 mutations. Mol Genet Metab 2011; 103:383-7. [PMID: 21636302 DOI: 10.1016/j.ymgme.2011.04.018] [Citation(s) in RCA: 60] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/29/2011] [Revised: 04/29/2011] [Accepted: 04/30/2011] [Indexed: 01/21/2023]
Abstract
INTRODUCTION Pathogenic mutations in the OPA1 gene are the most common identifiable cause of autosomal dominant optic atrophy (DOA), which is characterized by selective retinal ganglion cell loss, a distinctive pattern of temporal pallor of the optic nerve and a typical color vision deficit, with variable effects on visual acuity. Haploinsufficiency has been suggested as the major pathogenic mechanism for DOA. Here we present two siblings with severe ataxia, hypotonia, gastrointestinal dysmotility, dysphagia, and severe, early-onset optic atrophy who were found to be compound heterozygotes for two pathogenic OPA1 mutations. This example expands the clinical phenotype of OPA1-associated disorders and provides additional evidence for semi-dominant inheritance. METHODS AND RESULTS Molecular analysis of the OPA1 gene in this family by Sanger sequencing revealed compound heterozygosity for two mutations in trans configuration, a p.I382 M missense mutation and a p.V903GfsX3 frameshift deletion in both affected siblings. Electron microscopy of a skeletal muscle biopsy of the older sibling revealed dense osmiophilic bodies within the mitochondria. Mitochondrial DNA (mtDNA) content was within normal limits, and electron transport chain analysis showed no deficiencies of the mitochondrial respiratory chain enzymes. Multiple mtDNA deletions were not found. CONCLUSION Compound heterozygosity of pathogenic OPA1 mutations may cause severe neuromuscular phenotypes in addition to early-onset optic atrophy. While a role for OPA1 in mtDNA maintenance has been discussed, compound biallelic pathogenic OPA1 mutations in our patients did not result in altered mtDNA copy number, mtDNA deletions, or deficiencies of the electron transport chain, despite the severe clinical phenotype.
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Affiliation(s)
- Christian P Schaaf
- Department of Molecular and Human Genetics, Baylor College of Medicine, Houston, TX, USA
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Finsterer J, Stöllberger C. Oculopharyngodistal myopathy and acquired noncompaction. Neuromuscul Disord 2011; 21:523-4; author reply 524-5. [DOI: 10.1016/j.nmd.2011.04.002] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
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Finsterer J. Inherited mitochondrial neuropathies. J Neurol Sci 2011; 304:9-16. [PMID: 21402391 DOI: 10.1016/j.jns.2011.02.012] [Citation(s) in RCA: 43] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/18/2010] [Revised: 01/17/2011] [Accepted: 02/09/2011] [Indexed: 12/14/2022]
Abstract
Mitochondrial disorders (MIDs) occasionally manifest as polyneuropathy either as the dominant feature or as one of many other manifestations (inherited mitochondrial neuropathy). MIDs in which polyneuropathy is the dominant feature, include NARP syndrome due to the transition m.8993T>, CMT2A due to MFN2 mutations, CMT2K and CMT4A due to GDAP1 mutations, and axonal/demyelinating neuropathy with external ophthalmoplegia due to POLG1 mutations. MIDs in which polyneuropathy is an inconstant feature among others is the MELAS syndrome, MERRF syndrome, LHON, Mendelian PEO, KSS, Leigh syndrome, MNGIE, SANDO; MIRAS, MEMSA, AHS, MDS (hepato-cerebral form), IOSCA, and ADOA syndrome. In the majority of the cases polyneuropathy presents in a multiplex neuropathy distribution. Nerve conduction studies may reveal either axonal or demyelinated or mixed types of neuropathies. If a hereditary neuropathy is due to mitochondrial dysfunction, the management of these patients is at variance from non-mitochondrial hereditary neuropathies. Patients with mitochondrial hereditary neuropathy need to be carefully investigated for clinical or subclinical involvement of other organs or systems. Supportive treatment with co-factors, antioxidants, alternative energy sources, or lactate lowering agents can be tried. Involvement of other organs may require specific treatment. Mitochondrial neuropathies should be included in the differential diagnosis of hereditary neuropathies.
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The man who could not see what he could not eat. Surv Ophthalmol 2011; 56:461-5. [PMID: 21371731 DOI: 10.1016/j.survophthal.2010.11.007] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/11/2010] [Revised: 11/18/2010] [Accepted: 11/23/2010] [Indexed: 11/23/2022]
Abstract
A 55-year-old Hispanic man born in New Mexico presented with progressively worsening bilateral upper eyelid ptosis and dysphagia. External levator advancement 5 years before did not improve his ptosis. A thorough systemic workup for myasthenia gravis was negative, but electromyography suggested a myopathic process. Molecular genetic testing was positive for oculopharyngeal muscular dystrophy.
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Abstract
INTRODUCTION Chronic progressive external ophthalmoplegia (CPEO) is a mitochondrial syndrome on a disease spectrum with Kearns-Sayre syndrome (KSS). Clinical presentation is variable and our experience suggested that phenotypic differences exist in CPEO with onset after age 20. METHODS This descriptive study is a retrospective chart review of 40 patients with late-onset CPEO. Clinical features, laboratory and neurophysiology results were reviewed. RESULTS Multisystem dysfunction was very common in this series. Gastrointestinal dysfunction was more common than expected (60%) as was migraine headache (40%). Clinical characteristics on the KSS disease spectrum were uncommon in this series with only 2.5% having pigmentary retinopathy, 5% with cardiac conduction abnormality, and 22.5% having endocrinopathy (most often thyroid dysfunction rather than diabetes). Neurophysiology abnormalities included length-dependent axonal polyneuropathy in 44% (sometimes subclinical) and myopathic EMG changes in 26%. Exposure to sources of acquired mitochondrial toxicity including cigarette use and hepatitis C infection were more common than expected in this series. DISCUSSION Phenotype was different in this late-onset series compared with previous reports in CPEO patients. In this series of late-onset patients, multi-organ dysfunction was more common than previously reported in CPEO, and some classical mitochondrial manifestations, such as pigmentary retinopathy were rare. We suggest that acquired mitochondrial toxicity may have a role in the pathogenesis of adult-onset CPEO.
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Mehta AR, Fox SH, Tarnopolsky M, Yoon G. Mitochondrial mimicry of multiple system atrophy of the cerebellar subtype. Mov Disord 2011; 26:753-5. [PMID: 21259344 DOI: 10.1002/mds.23510] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/23/2010] [Revised: 09/22/2010] [Accepted: 10/11/2010] [Indexed: 11/08/2022] Open
Abstract
BACKGROUND We describe a patient with clinical and radiological findings suggestive of multiple system atrophy of the cerebellar subtype (MSA-C). METHODS/RESULTS Sequencing of the polymerase-γ 1 (POLG1) gene revealed the patient had compound heterozygous mutations of the POLG1 gene. Muscle biopsy revealed the presence of multiple mitochondrial DNA deletions and depletion, confirming the pathogenic nature of the POLG1 mutations. DISCUSSION This case expands the spectrum of phenotypes associated with POLG1 mutations to include multiple system atrophy and prompts further consideration regarding whether routine screening for POLG1 mutations is indicated in this patient population.
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Affiliation(s)
- Arpan R Mehta
- Movement Disorder Clinic, Toronto Western Hospital, University of Toronto, Toronto, Canada
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Schaller A, Hahn D, Jackson CB, Kern I, Chardot C, Belli DC, Gallati S, Nuoffer JM. Molecular and biochemical characterisation of a novel mutation in POLG associated with Alpers syndrome. BMC Neurol 2011; 11:4. [PMID: 21235791 PMCID: PMC3032677 DOI: 10.1186/1471-2377-11-4] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/20/2010] [Accepted: 01/14/2011] [Indexed: 12/24/2022] Open
Abstract
Background DNA polymerase γ (POLG) is the only known mitochondrial DNA (mtDNA) polymerase. It mediates mtDNA replication and base excision repair. Mutations in the POLG gene lead to reduction of functional mtDNA (mtDNA depletion and/or deletions) and are therefore predicted to result in defective oxidative phosphorylation (OXPHOS). Many mutations map to the polymerase and exonuclease domains of the enzyme and produce a broad clinical spectrum. The most frequent mutation p.A467T is localised in the linker region between these domains. In compound heterozygote patients the p.A467T mutation has been described to be associated amongst others with fatal childhood encephalopathy. These patients have a poorer survival rate compared to homozygotes. Methods mtDNA content in various tissues (fibroblasts, muscle and liver) was quantified using quantitative PCR (qPCR). OXPHOS activities in the same tissues were assessed using spectrophotometric methods and catalytic stain of BN-PAGE. Results We characterise a novel splice site mutation in POLG found in trans with the p.A467T mutation in a 3.5 years old boy with valproic acid induced acute liver failure (Alpers-Huttenlocher syndrome). These mutations result in a tissue specific depletion of the mtDNA which correlates with the OXPHOS-activities. Conclusions mtDNA depletion can be expressed in a high tissue-specific manner and confirms the need to analyse primary tissue. Furthermore, POLG analysis optimises clinical management in the early stages of disease and reinforces the need for its evaluation before starting valproic acid treatment.
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Affiliation(s)
- André Schaller
- Division of Human Genetics, University Hospital Bern, Bern, Switzerland.
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Abstract
Mitochondrial respiratory chain (RC) disorders (RCDs) are a group of genetically and clinically heterogeneous diseases because of the fact that protein components of the RC are encoded by both mitochondrial and nuclear genomes and are essential in all cells. In addition, the biogenesis, structure, and function of mitochondria, including DNA replication, transcription, and translation, all require nuclear-encoded genes. In this review, primary molecular defects in the mitochondrial genome and major classes of nuclear genes causing mitochondrial RCDs, including genes underlying mitochondrial DNA (mtDNA) depletion syndrome, as well as genes encoding RC subunits, complex assembly genes, and translation factors, are described. Diagnostic methodologies used to detect common point mutations, large deletions, and unknown point mutations in the mtDNA and to quantify mutation heteroplasmy are also discussed. Finally, the selection of nuclear genes for gold standard sequence analysis, application of novel technologies including oligonucleotide array comparative genomic hybridization, and massive parallel sequencing of target genes are reviewed.
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Affiliation(s)
- Lee-Jun C Wong
- Department of Molecular and Human Genetics, Baylor College of Medicine, One Baylor Plaza, Houston, TX 77030, USA.
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Abstract
The nervous system contains some of the body's most metabolically demanding cells that are highly dependent on ATP produced via mitochondrial oxidative phosphorylation. Thus, the neurological system is consistently involved in patients with mitochondrial disease. Symptoms differ depending on the part of the nervous system affected. Although almost any neurological symptom can be due to mitochondrial disease, there are select symptoms that are more suggestive of a mitochondrial problem. Certain symptoms that have become sine qua non with underlying mitochondrial cytopathies can serve as diagnostic "red-flags." Here, the typical and atypical presentations of mitochondrial disease in the nervous system are reviewed, focusing on "red flag" neurological symptoms as well as associated symptoms that can occur in, but are not specific to, mitochondrial disease. The multitudes of mitochondrial syndromes are not reviewed in-depth, though a select few are discussed in some detail.
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Affiliation(s)
- Sumit Parikh
- Neurogenetics and Metabolism, Cleveland Clinic, 9500 Euclid Avenue, Cleveland, OH 44195, USA.
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41
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Abstract
PURPOSE OF REVIEW The present review focuses on recent developments in diagnosis and treatment of sensory neuropathies. It does not seek to establish a comprehensive classification of sensory neuropathies, nor treatment guidelines per se. RECENT FINDINGS Diagnostic criteria and guidelines have been developed for distal symmetric polyneuropathies, small fiber sensory neuropathies and sensory neuronopathies. Novel diagnostic tools such as skin biopsies now allow diagnosis of small fiber sensory neuropathies. Genetic testing has defined new subtypes of mitochondrial neuropathies and inherited neuropathies with sensory involvement. Intravenous immunoglobulin and tumor necrosis factor-alpha inhibitors show promise for some dysimmune sensory neuropathies or neuronopathies. Additional options for management of neuropathic pain are emerging. SUMMARY Diagnostic methods for both acquired and hereditary sensory neuropathies have progressed in recent years, leading to earlier and more specific diagnoses and a better understanding of disease mechanisms. Much progress remains to be made regarding symptomatic and disease-modifying therapy for a range of sensory neuropathies, including those due to diabetes, HIV infection and from dysimmune or hereditary causes.
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Posada IJ, Gallardo ME, Domínguez C, Rivera H, Cabello A, Arenas J, Martín MA, Garesse R, Bornstein B. Depleción del ácido desoxirribonucleico mitocondrial y mutaciones de POLG en un paciente con neuropatía sensorial atáxica, disartria y oftalmoplejía. Med Clin (Barc) 2010; 135:452-5. [DOI: 10.1016/j.medcli.2010.03.031] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/18/2009] [Revised: 03/18/2010] [Accepted: 03/18/2010] [Indexed: 10/19/2022]
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43
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Wong LJC, Naviaux RK, Brunetti-Pierri N, Zhang Q, Schmitt ES, Truong C, Milone M, Cohen BH, Wical B, Ganesh J, Basinger AA, Burton BK, Swoboda K, Gilbert DL, Vanderver A, Saneto RP, Maranda B, Arnold G, Abdenur JE, Waters PJ, Copeland WC. Molecular and clinical genetics of mitochondrial diseases due to POLG mutations. Hum Mutat 2010; 29:E150-72. [PMID: 18546365 DOI: 10.1002/humu.20824] [Citation(s) in RCA: 209] [Impact Index Per Article: 14.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
Mutations in the POLG gene have emerged as one of the most common causes of inherited mitochondrial disease in children and adults. They are responsible for a heterogeneous group of at least 6 major phenotypes of neurodegenerative disease that include: 1) childhood Myocerebrohepatopathy Spectrum disorders (MCHS), 2) Alpers syndrome, 3) Ataxia Neuropathy Spectrum (ANS) disorders, 4) Myoclonus Epilepsy Myopathy Sensory Ataxia (MEMSA), 5) autosomal recessive Progressive External Ophthalmoplegia (arPEO), and 6) autosomal dominant Progressive External Ophthalmoplegia (adPEO). Due to the clinical heterogeneity, time-dependent evolution of symptoms, overlapping phenotypes, and inconsistencies in muscle pathology findings, definitive diagnosis relies on the molecular finding of deleterious mutations. We sequenced the exons and flanking intron region from approximately 350 patients displaying a phenotype consistent with POLG related mitochondrial disease and found informative mutations in 61 (17%). Two mutant alleles were identified in 31 unrelated index patients with autosomal recessive POLG-related disorders. Among them, 20 (67%) had Alpers syndrome, 4 (13%) had arPEO, and 3 (10%) had ANS. In addition, 30 patients carrying one altered POLG allele were found. A total of 25 novel alterations were identified, including 6 null mutations. We describe the predicted structural/functional and clinical importance of the previously unreported missense variants and discuss their likelihood of being pathogenic. In conclusion, sequence analysis allows the identification of mutations responsible for POLG-related disorders and, in most of the autosomal recessive cases where two mutant alleles are found in trans, finding deleterious mutations can provide an unequivocal diagnosis of the disease.
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Affiliation(s)
- Lee-Jun C Wong
- Department of Molecular and Human Genetics, Baylor College of Medicine, Houston, TX 77030, USA.
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44
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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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45
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Weiss MD, Saneto RP. Sensory ataxic neuropathy with dysarthria and ophthalmoparesis (SANDO) in late life due to compound heterozygous POLG mutations. Muscle Nerve 2010; 41:882-5. [PMID: 20513108 DOI: 10.1002/mus.21636] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Abstract
Missense mutations in the gene for polymerase gamma 1 (POLG1) cause a number of phenotypically heterogeneous mitochondrial diseases, most commonly progressive external ophthalmoplegia, and are characterized by the accumulation of multiple, large-scale deletions of mitochondrial DNA. The triad of sensory ataxic neuropathy, dysarthria, and ophthalmoparesis (SANDO) has been demonstrated in a small subset of patients with POLG1 mutations. We report a sporadic case of an 80-year-old compound heterozygote man who presented with SANDO and was found to have three known pathogenic mutations in the POLG1 gene (p.T251I/p.P587L/p.G848S). To our knowledge, none of these mutations have been demonstrated previously in SANDO. This patient's late presentation illustrates that a mitochondrial disorder should be considered regardless of age if the clinical symptoms warrant.
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Affiliation(s)
- Michael D Weiss
- Department of Neurology, University of Washington Medical Center, Box 356115, 1959 NE Pacific Street, Seattle, Washington 98195, USA.
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47
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McHugh JC, Lonergan R, Howley R, O'Rourke K, Taylor RW, Farrell M, Hutchinson M, Connolly S. Sensory ataxic neuropathy dysarthria and ophthalmoparesis (SANDO) in a sibling pair with a homozygous p.A467T POLG mutation. Muscle Nerve 2010; 41:265-9. [PMID: 19813183 DOI: 10.1002/mus.21494] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
Two siblings who developed fifth-decade-onset, concurrent progressive sensory ataxia, dysarthria, and ophthalmoparesis were found to be homozygous for the p.A467T mutation of the polymerase gamma (POLG) gene. The clinical course in both subjects was progression to severe disability. The enlarging spectrum of sensory ataxic neuropathies associated with mitochondrial DNA (mtDNA) instability and POLG mutations should be recognized and considered in the differential diagnosis of this unusual presentation.
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Affiliation(s)
- John C McHugh
- Department of Neurology, St. Vincent's University Hospital, Dublin, Ireland.
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48
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Achar P, Kumar B. Sensori-neural hearing loss in Sensory ataxic neuropathy, dysarthria and ophthalmoparesis (SANDO): A Case Report. Scott Med J 2010. [DOI: 10.1258/rsmsmj.55.1.57g] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Abstract
Objective To report a case of bilateral sensorineural hearing loss in a patient with sensory ataxic neuropathy, dysarthria and ophthalmoparesis (SANDO). Method Case report and review of literature on mitochondrial disorders to facilitate understanding of the type of hearing loss. Case report We present a 37 year old lady diagnosed with SANDO, who was seen in the ENT department with a history of progressive hearing loss for 6 months. Audiogram showed bilateral trough shaped sensorineural hearing loss, dipping at 1 KHz. Earlier, this patient had presented to the neurology department with classical neurological signs of progressive sensory ataxia. Diagnosis of SANDO was confirmed by muscle biopsy and mitochondrial studies. Conclusion This is the first case report on SANDO documenting associated hearing loss in ENT literature. Further studies are required to explain the pattern of hearing loss in these patients
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Affiliation(s)
- P Achar
- Department of ENT and Head Neck Surgery Royal Albert Edward Infirmary, Wrightington, Wigan &Leigh NHS Trust, Wigan lane, Wigan, WN1 2NN
| | - Bn Kumar
- Department of ENT and Head Neck Surgery Royal Albert Edward Infirmary, Wrightington, Wigan &Leigh NHS Trust, Wigan lane, Wigan, WN1 2NN
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Embiruçu EK, Martyn ML, Schlesinger D, Kok F. Autosomal recessive ataxias: 20 types, and counting. ARQUIVOS DE NEURO-PSIQUIATRIA 2009; 67:1143-56. [DOI: 10.1590/s0004-282x2009000600036] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/11/2009] [Accepted: 09/22/2009] [Indexed: 11/22/2022]
Abstract
More than 140 years after the first description of Friedreich ataxia, autosomal recessive ataxias have become one of the more complex fields in Neurogenetics. Currently this group of diseases contains more than 20 clinical entities and an even larger number of associated genes. Some disorders are very rare, restricted to isolated populations, and others are found worldwide. An expressive number of recessive ataxias are treatable, and responsibility for an accurate diagnosis is high. The purpose of this review is to update the practitioner on clinical and pathophysiological aspects of these disorders and to present an algorithm to guide the diagnosis.
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Affiliation(s)
| | | | - David Schlesinger
- University of São Paulo, Brazil; Universidade de São Paulo; Universidade de São Paulo
| | - Fernando Kok
- University of São Paulo, Brazil; Universidade de São Paulo
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50
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Abstract
Mitochondrial disorders (MIDs) are an increasingly recognized condition. The second most frequently affected organ in MIDs is the central nervous system. One of the most prevalent clinical CNS manifestations of MIDs is ataxia. Ataxia may be even the dominant manifestation of a MID. This is why certain MIDs should be included in the classification of heredoataxias or at least considered as differentials of classical heredoataxias. MIDs due to mutations of the mitochondrial DNA, which develop ataxia include the MERRF, NARP, MILS, or KSS syndrome. More rarely, ataxia may be a feature of MELAS, LHON, PS, MIDD, or MSL. MIDs due to mutations of the nuclear DNA, which develop ataxia include LS, SANDO, SCAE, AHS, XSLA/A, IOSCA, MIRAS, MEMSA, or LBSL syndrome. More rarely ataxia can be found in AD-CPEO, AR-CPEO, MNGIE, DIDMOAD, CoQ-deficiency, ADOAD, DCMA, or PDC-deficiency. MIDs most frequently associated with ataxia are the non-syndromic MIDs. Syndromic and non-syndromic MIDs with ataxia should be delineated from classical heredoataxias to initiate appropriate symptomatic or supportive treatment.
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