Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UMLS:C0027066 (myoclonus)
 4,275 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

A 73-year-old woman (patient 1) developed progressive mental deterioration at age 63, and seizures at age 70. On examination, she showed severe dementia, tonic clonic convulsion, hypotonia and muscular wasting. There was neither myoclonus nor cerebellar ataxia. Brain CT revealed a low density area in the right occipital lobe. A 44-year-old man (son of the patient 1) developed unsteady gait at age 15, muscle twitching at age 18 and then noticed speech disturbance at age 35. He had no history of convulsive seizure. Neurological examination showed cerebellar ataxia, myoclonus in the extremities and mild muscular weakness. His intelligence was normal. Brain CT showed moderate atrophy of the pons and the cerebellum. Both cases showed the same mitochondrial DNA mutation as reported previously in patients with MERRF. However, the clinical features, the age of onset and the brain CT findings were totally different between these 2 cases. In the progress of mitochondrial genetic analysis, atypical forms in MERRF like the patient 1 would increase in number, and the wide variation of clinical symptoms should be considered.
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PMID:[Two cases of MERRF (myoclonus epilepsy associated with ragged red fibers) showing different clinical features in the same family]. 812 82

We looked for the A-->G transition at position 8344 of mtDNA in 150 patients, most of them with diagnosed or suspected mitochondrial disease, to assess the specificity of this mutation for the MERRF phenotype, to define the clinical spectrum associated with the mutation, and to study the relationship between percentage of mutation in muscle and clinical severity. Our results confirm the high correlation between the A-->G transition at position 8344 and the MERRF syndrome, but they also show that this mutation can be associated with other phenotypes, including Leigh's syndrome, myoclonus or myopathy with truncal lipomas, and proximal myopathy. The absence of the mutation in four typical MERRF patients suggests that other mutations in the tRNA(Lys) gene, or elsewhere in the mitochondrial DNA, can produce the same phenotype.
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PMID:Clinical features associated with the A-->G transition at nucleotide 8344 of mtDNA ("MERRF mutation"). 817 May 67

We performed a 5-year clinical and electrophysiologic follow-up study on two sibling cases with myoclonus epilepsy with ragged-red fibers. Both had myoclonus, intention tremor, slight muscle weakness, slight mental disturbance, hearing impairment, and optic atrophy. Neither had epileptic attacks or truncal or gait ataxia. Biochemical activity of cytochrome c oxidase was at the lower limit of the normal range of values, and an adenine to guanine transition mutation at nucleotide 8344 in the transfer RNA specific for lysine of mitochondrial DNA was detected in both cases. The electroencephalograms showed slowing of basic patterns, diffuse spike-and-wave complexes, occipital dominant wave-and-spike phantoms, 6- and 14-Hz positive spikes, and photosensitivity. No definite deterioration of basic patterns was seen, and diffuse spike-and-wave complexes and photosensitivity gradually disappeared during the slowly progressive clinical course. P2 latencies of pattern-reversal visual evoked potentials throughout the clinical course and III through V interpeak latencies of auditory brainstem responses at follow-up were prolonged without giant sensory evoked potentials in both cases.
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PMID:Myoclonus epilepsy with ragged-red fibers: a clinical and electrophysiologic follow-up study on two sibling cases. 822 33

We report myoclonic epilepsy with ragged-red fibers (MERRF) syndrome in a Chinese family with confirmed mitochondrial DNA point mutation. Six members of the family including the grandmother, two siblings, and three grandchildren were affected. Among them, action myoclonus was seen in five; short stature, muscle weakness, and mental retardation in four; lactic acidosis, hearing impairment, and ataxia in two; and seizures in one. Muscle biopsy from two affected siblings revealed ragged-red fibers and abundant subsarcolemmal mitochondria with paracrystalline inclusions. Pedigree analysis suggests a maternal transmission. Analysis of mitochondrial DNA showed a point mutation from A to G at the 8344th nucleotide position located in the tRNA(Lys) gene. To our knowledge, this is the first report of MERRF syndrome with such genetic defect from a Chinese family. The present and previous reports support the notion that mitochondrial DNA point mutation at the 8344th nucleotide position is the most common cause of MERRF syndrome.
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PMID:Myoclonic epilepsy with ragged-red fibers (MERRF) syndrome: report of a Chinese family with mitochondrial DNA point mutation in tRNA(Lys) gene. 793 36

The chromosomal loci for seven epilepsy genes have been identified in chromosomes 1q, 6p, 8q, 16p, 20q, 21q, and 22q. In 1987, the first epilepsy locus was mapped in a common benign idiopathic generalized epilepsy syndrome, juvenile myoclonic epilepsy (JME). Properdin factor or Bf, human leukocyte antigen (HLA), and DNA markers in the HLA-DQ region were genetically linked to JME and the locus, named EJM1, was assigned to the short arm of chromosome 6. Our latest studies, as well as those by Whitehouse et al., show that not all families with JME have their genetic locus in chromosome 6p, and that childhood absence epilepsy does not map to the same EJM1 locus. Recent results, therefore, favor genetic heterogeneity for JME and for the common idiopathic generalized epilepsies. Heterogeneity also exists in benign familial neonatal convulsions, a rare form of idiopathic generalized epilepsy. Two loci are now recognized; one in chromosome 20q (EBN1) and another in chromosome 8q. Heterogeneity also exists for the broad group of debilitating and often fatal progressive myoclonus epilepsies (PME). The gene locus (EPM1) for both the Baltic and Mediterranean types of PME or Unverricht-Lundborg disease is the same and is located in the long arm of chromosome 21. Lafora type of PME does not map to the same EPM1 locus in chromosome 21. PME can be caused by the juvenile type of Gaucher's disease, which maps to chromosome 1q, by the juvenile type of neuronal ceroid lipofuscinoses (CLN3), which maps to chromosome 16p, and by the "cherry-red-spot-myoclonus" syndrome of Guazzi or sialidosis type I, which has been localized to chromosome 10. A point mutation in the mitochondrial tRNA(Lys) coding gene can also cause PME in children and adults (MERFF).
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PMID:Progress in mapping human epilepsy genes. 829 22

We describe a 42-year-old woman with overlapping syndrome of MELAS (mitochondrial myopathy, encephalopathy, lactic acidosis and stroke-like episodes) and MERRF (myoclonus epilepsy and ragged-red fibers). Clinically, she had episodic headache, stroke-like episode with left hemiparesis and lactic acidosis commonly found in MELAS syndrome. However, myoclonus seizure, and ataxia with dyssynergic gait characteristic of MERRF were also noted. Computed tomographic scans showed a right temporo-parietal hypodense lesion. The lesion disappeared 20 months later, even magnetic resonance images also failed to reveal this abnormality. A molecular analysis of mitochondrial DNA was conducted by using restriction endonucleases ApaI and NaeI. A transition from A to G was found at the nucleotide position 3243, but not found at the 8344th nucleotide pair. In this report, we document the fluctuating CT changes and emphasize the importance of molecular analysis in patients with overlapping syndrome of mitochondrial encephalomyopathies.
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PMID:Overlapping syndrome of MERRF and MELAS: molecular and neuroradiological studies. 835 81

Recent advances in molecular genetics have led to a better understanding of mitochondrially inherited diseases. Mitochondrial encephalomyopathy overlap syndrome is one such group of diseases in which ocular abnormalities are frequently manifest. The authors describe the clinical, molecular genetic, and pathologic findings of two patients with the mitochondrial encephalomyopathy overlap syndrome. The patients shared a similar clinical course with features overlapping the three traditionally distinct clinical phenotypes (the Kearns-Sayre syndrome; the syndrome of mitochondrial encephalopathy, lactic acidosis, and stroke [MELAS], and the syndrome of myoclonus, epilepsy, and ragged red fibers [MERRF]). The patients had identical mitochondrial DNA mutations (at nucleotide position 3243) and had similar ultrastructural abnormalities, including abundant enlarged mitochondria with "whorled" and "tubular" cristae. These abnormal mitochondria appeared to be preferentially distributed in cells with high metabolic activity (retinal pigment epithelium, corneal endothelium, and extraocular muscles).
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PMID:Ocular clinicopathologic study of the mitochondrial encephalomyopathy overlap syndromes. 836 69

Six months after the onset of visual loss a 23-year-old male patient with Leber's optic neuropathy associated with a mitochondrial DNA mutation developed brain stem involvement with Parinaud's syndrome and oculopalatal myoclonus. Magnetic resonance imaging (MRI) revealed a high signal area in the brain stem, corresponding to a hypodense area in the CT scan that did not show contrast enhancement. Distinct diminution but not complete remission of the MRI findings was found in the 5-year follow-up, which was not accompanied by clinical improvement. Although the MRI findings were compatible with a demyelinating lesion, neither extensive evoked potential studies nor spinal fluid examination supported this.
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PMID:Central nervous system involvement in Leber's optic neuropathy. 849 15

The mitochondrial DNA (mtDNA) transfer RNA (tRNA)Lys A-->G(8344) mutation was identified in seven patients. These patients and their relatives were assessed clinically; in one family the mutation was deduced to be present in four generations. The phenotype in index cases was consistent with the syndrome of myoclonic epilepsy with ragged red fibres, with the core clinical features of myoclonus, ataxia and seizures. Amongst other features, progressive external ophthalmoplegia, Leigh's syndrome and stroke-like episodes were observed, well recognized in mitochondrial myopathies but novel manifestations of this genotype. Samples of blood and muscle were analysed for the proportion of mutant mtDNA using an oligonucleotide hybridization technique. The proportion of mutant mtDNA in blood was significantly greater in symptomatic than asymptomatic cases. Furthermore, the proportion of mutant mtDNA in blood correlated with age of onset of disease and clinical severity assessed by a simple scale. Study of disease associated with the tRNA(Lys) A-->G(8344) mutation provides further insight into the pathogenesis and transmission of mitochondrial diseases. Quantification of the proportion of mtDNA in tissues demonstrates that this is a major factor determining the course of disease, but other, as yet unidentified factors are also likely to play a role.
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PMID:The mitochondrial DNA transfer RNA(Lys)A-->G(8344) mutation and the syndrome of myoclonic epilepsy with ragged red fibres (MERRF). Relationship of clinical phenotype to proportion of mutant mitochondrial DNA. 851 95

Ten patients, two men and eight women with mitochondrial encephalomyopathy, had an A-G mutation at nucleotide pair 8,344 in the mitochondrial DNA, the most common genetic defect in myoclonus epilepsy with ragged-red fibers (MERRF). Eight patients had the clinical and pathologic characteristics of MERRF including myoclonus, seizures, cerebellar ataxia and myopathy with ragged-red fibers. Two patients had atypical symptoms such as early onset of fatal cardiac failure and late onset of rapid mental deterioration, respectively. The striking feature in our patients with the 8,344 mutation cardiac involvement and two developed progressive heart failure. In the typical MERRF patients, the proportion of mutant mitochondrial DNA in their skeletal muscles, quantified by a single strand conformation polymorphism analysis, was above 85%. However, there was no significant correlation between clinical severity, histopathological findings and the proportion of mutant mtDNA in muscle biopsy samples, suggesting that non-ragged-red fibers play an important role in the phenotype expression of the mutants.
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PMID:The 8,344 mutation in mitochondrial DNA: a comparison between the proportion of mutant DNA and clinico-pathologic findings. 858 Jul 30


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