Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UMLS:C0162671 (MELAS)
 587 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

A 30-year-old man was hospitalized with dysarthria and weakness of his right arm and leg. Three months previously, he had noticed numbness and weakness of his right shoulder, which spread to involve his left leg but which improved after 8 months. On admission, neurological examination revealed limb kinetic apraxia and constructive apraxia of the right hand, motor aphasia, dysarthria, and spastic quadriplegia. Sensory examination revealed hyperalgesia and dysesthesia in the right arm and left leg. Deep tendon reflexes were hyperactive in all four extremities. And he had bilateral Babinski signs. Laboratory examination revealed pH 7.38, PCO2 46.1 Torr, PO2 93.4 Torr, BE 1.7, and blood lactate, 9.0 mg/dl (normal 5-20 mg/dl). Cerebrospinal fluid lactate level was 20.0 mg/dl. pyruvate 1.34 mg/dl. and protein 83 mg/dl. Blood lactate and pyruvate values were markedly elevated after aerobic exercise. T2WI brain MRI showed scattered high signal lesions in the left precentral and postcentral gyrus, right paracentral lobes, both superior frontal gyri, and right superior temporal gyrus. Right biceps brachi biopsy showed almost complete cytochrome c oxidase (COX) deficiency. There were no ragged-red fibers. There was marked decrease of COX activity: 2.7 nmol/min/mg-mitochondrial protein (normal range: 33.0 +/- 16.1, n = 7) in the biopsied muscle. Open brain biopsy (after permission from the patient and his family) revealed gliosis and perivascular infiltration of lymphocytes and macrophages without vascular proliferation. There was no mitochondrial DNA mutations, deletion or duplication, including tRNA-Leu 3243, 8993, 3271, 9176, 3291, and tRNA-Lys 8344, 8356, and 8363. From these findings, a diagnosis of COX deficiency presenting as MELAS-like episodes was done. His mother also showed abnormality on aerobic exercise test, but she had no episode of stroke or neurological dysfunction. Six months later, his aphasia and apraxia of the right hand had resolved, and at discharge he was able to ambulate with a cane. Ten months later, he returned to his work. There has been no recurrence of neurologic symptoms over the next 3 years and 10 months. This patient appears to represent a rare case of adult onset COX deficiency presenting as MELAS-like episodes.
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PMID:[MELAS-like episodes in an adult case with cytochrome c oxidase deficiency]. 1523 72

Mitochondrial cytopathy is a heterogeneous group of disorders with a wide range of clinical features. To evaluate the incidence and clinical heterogeneity of A3243G mitochondrial tRNA mutation in the Korean population, we evaluated patients who were clinically suggestive of having mitochondrial encephalomyopathy. Eighty-five patients were included in this study. All showed clinical features of mitochondrial encephalomyopathy and had three or more of the following clinical manifestations: (1) psychomotor regression, (2) hyperlacticacidemia, (3) recurrent stoke-like episodes, (4) idiopathic cardiomyopathy, (5) sensoryneural hearing loss, (6) diabetes mellitus, (7) myopathy, (8) renal disease and (9) relatives with known mitochondrial disease. The patients were clinically classified as MELAS, MERRF, Leigh syndrome, Kearns-Sayre syndrome, chronic progressive external ophthalmoplegia and uncertain. Of the 85 patients, 19 had the A3243G mutation (22.3%). Thirty-one patients showed typical clinical characteristics of MELAS. Fourteen of those 31 patients had A3243G mutation (45.1%). Four patients harboring A3243G mutations showed atypical and heterogeneous clinical features, unlike MELAS. This study revealed the frequent occurrence of A3243G mutation in Korean patients with mitochondrial disorders and their clinical features can be heterogeneous. It will be helpful to screen the presence of A3243G mutation for the genetic diagnosis of mitochondrial encephalomyopathy in Korea.
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PMID:Clinical features of A3243G mitochondrial tRNA mutation. 1535 Oct 82

Point mutations in mitochondrial (mt) tRNA genes are associated with a variety of human mitochondrial diseases. We have shown previously that mt tRNA(Leu(UUR)) with a MELAS A3243G mutation and mt tRNA(Lys) with a MERRF A8344G mutation derived from HeLa background cybrid cells are deficient in normal taurine-containing modifications [taum(5)(s(2))U; 5-taurinomethyl-(2-thio)uridine] at the anticodon wobble position in both cases. The wobble modification deficiency results in defective translation. We report here wobble modification deficiencies of mutant mt tRNAs from cybrid cells with different nuclear backgrounds, as well as from patient tissues. These findings demonstrate the generality of the wobble modification deficiency in mutant tRNAs in MELAS and MERRF.
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PMID:Wobble modification deficiency in mutant tRNAs in patients with mitochondrial diseases. 1589 15

Brain single photon emission computed tomography (SPECT) studies were conducted in three patients with A3243G mutation of the mitochondrial (mt) DNA tRNA. All were born to mothers suffering from chronic progressive external ophthalmoplegia (CPEO) with the same A3243G point mutation of the mtDNA tRNA. The first case manifested clinically with MELAS, the second case manifested with CPEO, and third case was characterized by recurrent migraine-like headache, tremor, and epilepsy. Brain SPECT of all patients, regardless of whether they had or had not suffered from stroke-like episodes, showed multiple areas of asymmetrical decreased perfusion, particularly in the posterior and lateral head regions, especially the temporal lobes. Crossed-cerebellar diaschisis may occur. Conventional brain magnetic resonance images failed to show some of the lesions. Decreased regional cerebral blood flow, rather than previously proposed hyperemia, is likely to be the cause. We conclude that mitochondrial vasculopathy with regional cerebral hypoperfusion may be seen on brain SPECT in patients with mitochondrial disorders and A3243G mutations, regardless of whether they have or have not suffered from stroke-like episodes.
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PMID:Brain single photon emission computed tomography in patients with A3243G mutation in mitochondrial DNA tRNA. 1596 44

The COII/tRNA(Lys) intergenic 9-bp deletion (MIC9D) of mitochondrial DNA (mtDNA) has been established as a genetic polymorphism for Asian-Pacific populations. We investigated whether this small mtDNA deletion is co-transmitted with human diseases such as mitochondrial encephalomyopathy with lactic acidosis and stroke-like episodes (MELAS) and myoclonic epilepsy with ragged-red fibers (MERRF) syndromes. Forty unrelated Taiwanese families, including 12 families with MERRF and A8344G mtDNA mutation and 28 families with MELAS and A3243G mutation of mtDNA, respectively, were recruited in this study. In addition, 199 healthy subjects were recruited as control. We found that the frequency of occurrence of mtDNA with the MIC9D polymorphism in healthy subjects was 21% (41/199). However, the incidence of the MIC9D polymorphism was 67% (8/12) among the probands of all the families with MERRF syndrome (P = 0.001; OR = 8) and 39% (11/28) among the probands of the families with MELAS syndrome (P = 0.038; OR = 2). This finding indicates that the frequency of occurrence of mtDNA with the MIC9D polymorphism in patients with MERRF or MELAS syndrome is higher than that of healthy subjects. The prevalence of mitochondrial encephalomyopathies in relation to the MIC9D polymorphism of mtDNA in Taiwanese population is discussed.
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PMID:High prevalence of the COII/tRNA(Lys) intergenic 9-bp deletion in mitochondrial DNA of Taiwanese patients with MELAS or MERRF syndrome. 1596 49

By purifying mutant mitochondrial tRNAs, we were able to ascertain that post-transcriptional modification at the anticodon wobble uridine is absent in tRNA(Lys) with the 8344 MERRF mutation and in tRNA(Leu(UUR)) with either the 3243 or 3271 MELAS mutation. Both the MERRF and MELAS mutant tRNAs substantially lost their translational ability, the extent of the loss in each mutant corresponding to the reduction in actual mitochondrial translational activity. Lack of the wobble modification deprived mutant tRNA(Lys) of interaction with the cognate codons. These features indicate that the modification defect plays a primary role in the molecular pathophysiology of these mitochondrial diseases.
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PMID:Wobble modification defect suppresses translational activity of tRNAs with MERRF and MELAS mutations. 1612 Mar 15

Maternal diabetes associated with neural deafness is designated as MIDD (maternal inherited diabetes and deafness); it is linked to a A3243G tRNA leucine gene mutation. The disease course is progressive and involvement of other systems is frequent. In most cases, macular pattern dystrophy is present. Muscular lesions are characteristic of mitochondrial myopathies. Mitochondrial abnormalities have also been observed in pancreas, heart, kidney, smooth muscle of the digestive tract with variable heteroplasmy levels. MIDD may present as a single syndrome or is part of MELAS or Kearns-Sayre syndrome.
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PMID:[Diabetes and mitochondrial cytopathies: pathological studies]. 1632 55

Lactic acidosis has been associated with a variety of clinical conditions and can be due to mutation in nuclear or mitochondrial genes. We performed mutations screening of all mitochondrial tRNA genes in 44 patients who referred as hyperlactic acidosis. Patients showed heterogeneous phenotypes including Leigh disease in four, MELAS in six, unclassified mitochondrial myopathy in 10, cardiomyopathy in five, MERRF in one, pure lactic acidosis in six, and others in 12 including facio-scaplo-femoral muscular dystrophy (FSFD), familial cerebellar ataxia, recurrent Reye syndrome, cerebral palsy with mental retardation. We measured enzymatic activities of pyruvate dehydrogenase complex, and respiratory chain enzymes. All mitochondrial tRNA genes and known mutation of ATPase 6 were studied by single strand conformation polymorphism (SSCP), automated DNA sequence and PCR-RFLP methods. We have found one patient with PDHC deficiency and six patients with Complex I+IV deficiency, though the most of the patients showed subnormal to deficient state of respiratory chain enzyme activities. We have identified one of the nucleotide changes in 29 patients. Single nucleotide changes in mitochondrial tRNA genes are found in 27 patients and one in ATPase 6 gene in two patients. One of four pathogenic point mutations (A3243G, C3303T, A8348G, and T8993G) was identified in 12 patients who showed the phenotype of Leigh syndrome, MELAS, cardimyopathy and cerebral palsy with epilepsy. Seventeen patients have one of the normal polymorphisms in the mitochondrial tRNA gene reported before. SSCP and PCR-RFLP could detect the heteroplasmic condition when the percentage of mutant up to 5, however, it cannot be observed by direct sequencing method. It is important to screen the mtDNA mutation not only by direct sequence but also by PCR-RFLP and the other sensitive methods to detect the heroplasmy when lactic acidosis has been documented in the patients who are not fulfilled the criteria of mitochondrial disorders.
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PMID:Mitochondrial tRNA gene mutations in patients having mitochondrial disease with lactic acidosis. 1633 22

The A3243G mutation in the mitochondrial gene for human mitochondrial (mt) tRNA(Leu(UUR)), responsible for decoding of UUR codons, is associated with mitochondrial myopathy, encephalopathy, lactic acidosis and stroke-like episodes (MELAS). We previously demonstrated that this mutation causes defects in 5-taurinomethyluridine (taum(5)U) modification at the anticodon first (wobble) position of the mutant mt tRNA(Leu(UUR)), leading to a UUG decoding deficiency and entraining severe respiratory defects. In addition, we previously identified a heteroplasmic mutation, G12300A, in the other mt leucine tRNA gene, mt tRNA(Leu(CUN)), which functions as a suppressor of the A3243G respiratory defect in cybrid cells containing A3243G mutant mtDNA. Although the G12300A mutation converts the anticodon sequence of mt tRNA(Leu(CUN)) from UAG to UAA, this tRNA carrying an unmodified wobble uridine still cannot decode the UUG codon. Mass spectrometric analysis of the suppressor mt tRNA(Leu(CUN)) carrying the G12300A mutation from the phenotypically revertant cells revealed that the wobble uridine acquires de novo taum(5)U modification. In vitro translation confirmed the functionality of the suppressor tRNA for decoding UUG codons. These results demonstrate that the acquisition of the wobble modification in another isoacceptor tRNA is critical for suppressing the MELAS mutation, and they highlight the primary role of the UUG decoding deficiency in the molecular pathogenesis of MELAS syndrome.
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PMID:Acquisition of the wobble modification in mitochondrial tRNALeu(CUN) bearing the G12300A mutation suppresses the MELAS molecular defect. 1644 7

Mitochondrial encephalomyopathies are a multisystemic group of disorders that are characterised by a wide range of biochemical and genetic mitochondrial defects and variable modes of inheritance. Among this group of disorders, the mitochondrial myopathy, encephalopathy, lactic acidosis with stroke-like episodes (MELAS) syndrome is one of the most frequently occurring, maternally inherited mitochondrial disorders. As the name implies, stroke-like episodes are the defining feature of the MELAS syndrome, often occurring before the age of 15 years. The clinical course of this disorder is highly variable, ranging from asymptomatic, with normal early development, to progressive muscle weakness, lactic acidosis, cognitive dysfunction, seizures, stroke-like episodes, encephalopathy and premature death. This syndrome is associated with a number of point mutations in the mitochondrial DNA, with over 80% of the mutations occurring in the dihydrouridine loop of the mitochondrial transfer RNA(Leu(UUR)) [tRNA(Leu)((UUR))] gene. The pathophysiology of the disease is not completely understood; however, several different mechanisms are proposed to contribute to this disease. These include decreased aminoacylation of mitochondrial tRNA, resulting in decreased mitochondrial protein synthesis; changes in calcium homeostasis; and alterations in nitric oxide metabolism. Currently, no consensus criteria exist for treating the MELAS syndrome or mitochondrial dysfunction in other diseases. Many of the therapeutic strategies used have been adopted as the result of isolated case reports or limited clinical studies that have included a heterogeneous population of patients with the MELAS syndrome, other defects in oxidative phosphorylation or lactic acidosis due to disorders of pyruvate metabolism. Current approaches to the treatment of the MELAS syndrome are based on the use of antioxidants, respiratory chain substrates and cofactors in the form of vitamins; however, no consistent benefits have been observed with these treatments.
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PMID:The mitochondrial myopathy encephalopathy, lactic acidosis with stroke-like episodes (MELAS) syndrome: a review of treatment options. 1673 97


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