Independent origin for m.3243A>G mitochondrial mutation in three Venezuelan cases of MELAS syndrome.

Mitochondrial myopathy, encephalopathy, lactic acidosis, and stroke-like episodes (MELAS) is a multisystem and progressive neurodegenerative mitochondrial disease, caused by point nucleotide changes in the mtDNA where 80 % of cases have the mutation m.3243A>G in the MT-TL1 gene. In this work, we described the clinical, biochemical and molecular analysis of three Venezuelan patients affected with MELAS syndrome. All cases showed lactic acidosis, cortical cerebral atrophy on magnetic resonance imaging and muscular system deficit, and in two of the cases alteration of urine organic acid levels was also registered. A screening for the mutation m.3243A>G in different patients' body samples confirmed the presence of this mutation with variable degrees of heteroplasmy (blood = 7-41 %, buccal mucosa = 14-53 %, urine = 58-94 %). The mitochondrial haplogroups for the three patients were different (H, C1b, and A2), indicating an independent origin for the mutation.

Acetyl-CoA-driven respiration in frozen muscle contributes to the diagnosis of mitochondrial disease.

BACKGROUND: Freezing human biopsies is common in clinical practice for storage. However, this technique disrupts mitochondrial membranes, hampering further analyses of respiratory function. To contribute to laboratorial diagnosis of mitochondrial diseases, this study sought to develop a respirometry approach using O2k (Oroboros Ins.) to measure the whole electron transport chain (ETC) activity in homogenates of frozen skeletal muscle biopsies. PATIENTS AND METHODS: We enrolled 16 patients submitted to muscle biopsy in the process of routine diagnostic investigation: four with mitochondrial disease and severe mitochondrial dysfunction; seven with exercise intolerance and multiple deletions of mitochondrial DNA, presenting mild to moderate mitochondrial dysfunction; five without mitochondrial disease, as controls. Whole homogenates of muscle fragments were prepared using grinder-type equipment. O2 consumption rates were normalized using citrate synthase activity. RESULTS: Transmission electron microscopy confirmed mitochondrial membrane discontinuation, indicating increased permeability of mitochondrial membranes in homogenates from frozen biopsies. O2 consumption rates in the presence of acetyl-CoA lead to maximum respiratory rates sensitive to rotenone, malonate and antimycin. This protocol of acetyl-CoA-driven respiration (ACoAR), applied in whole homogenates of frozen muscle, was sensitive enough to identify ETC abnormality, even in patients with mild to moderate mitochondrial dysfunction. We demonstrated adequate repeatability of ACoAR and found significant correlation between O2 consumption rates and enzyme activity assays of individual ETC complexes. CONCLUSIONS: We present preliminary data on a simple, low cost and reliable procedure to measure respiratory function in whole homogenates of frozen skeletal muscle biopsies, contributing to diagnosis of mitochondrial diseases in humans.

MELAS en el Perú: reporte de caso / MELAS in Peru: case report

El síndrome de MELAS es una rara citopatía mitocondrial de difícil diagnóstico. Reportamos el caso de una niña de 10 años, que ingresó al Instituto Nacional de Ciencias Neurológicas de Lima, Perú, quien presentó episodios bruscos similares a accidentes cerebrovasculares y crisis epilépticas. Los estudios de neuroimágenes mostraron infartos y el examen genético fue positivo para MELAS identificando la mutación más frecuente A3243G...

MELAS syndrome is a rare mitochondrial cytopathy difficult to diagnose. We report the case of a 10 year old girl who was admitted to the National Institute of Neurological Sciences of Lima - Peru, who presented sudden stroke like episodes and seizures. Neuroimaging studies showed infarction and genetic testing was positive for identifying the most common MELAS mutation (A3243)...

When should MELAS (Mitochondrial myopathy, Encephalopathy, Lactic Acidosis, and Stroke-like episodes) be the diagnosis? / Quando o diagnóstico deveria ser MELAS (Miopatia mitocondrial, encefalopatia, acidose lática, e episódios semelhantes a acidente vascular cerebral)?

ABSTRACTMitochondrial myopathy, Encephalopathy, Lactic Acidosis, and Stroke-like episodes (MELAS) is a rare mitochondrial disorder. Diagnostic criteria for MELAS include typical manifestations of the disease: stroke-like episodes, encephalopathy, evidence of mitochondrial dysfunction (laboratorial or histological) and known mitochondrial DNA gene mutations. Clinical features of MELAS are not necessarily uniform in the early stages of the disease, and correlations between clinical manifestations and physiopathology have not been fully elucidated. It is estimated that point mutations in the tRNALeu(UUR) gene of the DNAmt, mainly A3243G, are responsible for more of 80% of MELAS cases. Morphological changes seen upon muscle biopsy in MELAS include a substantive proportion of ragged red fibers (RRF) and the presence of vessels with a strong reaction for succinate dehydrogenase. In this review, we discuss mainly diagnostic criterion, clinical and laboratory manifestations, brain images, histology and molecular findings as well as some differential diagnoses and current treatments.

RESUMOMiopatia mitocondrial, encefalopatia, acidose lática, e episódios semelhantes a acidente vascular cerebral (MELAS) é uma rara doença mitocondrial. Os critérios diagnósticos para MELAS incluem as manifestações típicas da doença: episódios semelhantes a acidente vascular cerebral, encefalopatia, evidência de disfunção mitocondrial (laboratorial ou histológica) e mutação conhecida em genes do DNA mitocondrial. Na fase inicial da doença, as manifestações clínicas podem não ser uniformes, e sua correlação com a fisiopatologia não está completamente elucidada. Estima-se que as mutações de ponto no gene tRNALeu(UUR) do DNAmt, principalmente a A3243G, sejam responsáveis por cerca de 80% dos casos de MELAS. As alterações morfológicas na biópsia muscular incluem uma grande proporção de fibras vermelhas rasgadas (RRF) e presença de vasos com forte reação para succinato desidrogenase. Nesta revisão, são discutidos os principais critérios diagnósticos, manifestações clínicas e laboratoriais, imagens cerebrais, padrões eletrofisiológicos, histológicos e alterações moleculares, bem como alguns dos diagnósticos diferenciais e tratamentos atuais.

When should MELAS (Mitochondrial myopathy, Encephalopathy, Lactic Acidosis, and Stroke-like episodes) be the diagnosis?

Mitochondrial myopathy, Encephalopathy, Lactic Acidosis, and Stroke-like episodes (MELAS) is a rare mitochondrial disorder. Diagnostic criteria for MELAS include typical manifestations of the disease: stroke-like episodes, encephalopathy, evidence of mitochondrial dysfunction (laboratorial or histological) and known mitochondrial DNA gene mutations. Clinical features of MELAS are not necessarily uniform in the early stages of the disease, and correlations between clinical manifestations and physiopathology have not been fully elucidated. It is estimated that point mutations in the tRNALeu(UUR) gene of the DNAmt, mainly A3243G, are responsible for more of 80% of MELAS cases. Morphological changes seen upon muscle biopsy in MELAS include a substantive proportion of ragged red fibers (RRF) and the presence of vessels with a strong reaction for succinate dehydrogenase. In this review, we discuss mainly diagnostic criterion, clinical and laboratory manifestations, brain images, histology and molecular findings as well as some differential diagnoses and current treatments.

Espectro clínico de pacientes con hallazgos histopatológicos y/o moleculares compatibles con enfermedad mitochondrial / Clinical spectrum of patients with histopathological and/or molecular findings compatible with mitochondrial disease

Objetivo: Describir el espectro clínico de pacientes con diagnóstico definitivo de Enfermedad Mitocondrial, y su correlación con hallazgos bioquímicos, neuroimagenológicos, neuropatológicos, y moleculares. Método: Se revisaron las historias clínicas de pacientes con Enfermedad Mitocondrial evaluados durante el período 1990-2011. Resultados: Se incluyeron 41 pacientes, con una edad media inicial de 3,7 años. Identificamos cuatro grupos:1) Síndromes clásicos (65%): a) MELAS del inglés “Mitochondrial encephalomyopathy, lacticacidosis, and stroke-like episodes”, (diez), b) Síndrome de Leigh (diez) c) Síndrome de Kearns –Sayre (cinco), d) PEO del inglés “Progressive External Ophthalmoplegia” plus (OEP plus) (dos), 2) Miopatía: nueve (21,5%) 3) Encefalomiopatías inespecíficas: cinco (12%). Se realizó biopsia muscular en 37 pacientes. Un 70% evidenció fibras rojo rasgadas, cuatro (10,5%) fibras citocromo oxidasa negativas y ocho (14,7%) incremento de la actividad oxidativa subsarcolemal y en la microscopia electrónica alteraciones del tamaño y número de mitocondrias. En 14 se completaron estudios moleculares: Siete presentaron una mutación puntual A3243G en el ADN mitocondrial (MELAS), un paciente una mutación en el ADN mitocondrial A1351G (Síndrome de Leigh) y un paciente una deleción del ADN mitocondrial (OEP plus). Conclusiones: Se pudo corroborar la existencia en nuestro medio de síndromes asociados a patología mitocondrial tradicionalmente reconocidos. Un grupo de pacientes con encefalomiopatías denominadas inespecíficas presentaron un cuadro clínico variable, hallazgos de laboratorio y de imágenes poco orientadores y fue la sospecha de una enfermedad mitocondrial lo que nos llevó a realizar la biopsia que finalmente fue diagnóstica. Es posible que este grupo sea más numeroso y las limitaciones que implica realizar una biopsia muscular se facilite con los estudios moleculares.

MELAS: clinical features, muscle biopsy and molecular genetics.

OBJECTIVE: The aim of the study was to analyze a series of Brazilian patients suffering from MELAS. METHOD: Ten patients with MELAS were studied with correlation between clinical findings, laboratorial data, electrophysiology, histochemical and molecular features. RESULTS: Blood lactate was increased in eight patients. Brain image studies revealed a stroke-like pattern in all patients. Muscle biopsy showed ralled-red fibers (RRF) in 90% of patients on modified Gomori-trichrome and in 100% on succinate dehydrogenase stains. Cytochrome c oxidase stain analysis indicated deficient activity in one patient and subsarcolemmal accumulation in seven patients. Strongly succinate dehydrogenase-reactive blood vessels (SSV) occurred in six patients. The molecular analysis of tRNA (Leu(UUR)) gene by PCR/RLFP and direct sequencing showed the A3243G mutation on mtDNA in 4 patients. CONCLUSION: The muscle biopsy often confirmed the MELAS diagnosis by presence of RRF and SSV. Molecular analysis of tRNA(Leu(UUR)) gene should not be the only diagnostic criteria for MELAS.

MELAS: clinical features, muscle biopsy and molecular genetics / MELAS: manifestações clínicas, biópsia muscular e estudo molecular

OBJECTIVE: The aim of the study was to analyze a series of Brazilian patients suffering from MELAS. METHOD: Ten patients with MELAS were studied with correlation between clinical findings, laboratorial data, electrophysiology, histochemical and molecular features. RESULTS: Blood lactate was increased in eight patients. Brain image studies revealed a stroke-like pattern in all patients. Muscle biopsy showed ralled-red fibers (RRF) in 90 percent of patients on modified Gomori-trichrome and in 100 percent on succinate dehydrogenase stains. Cytochrome c oxidase stain analysis indicated deficient activity in one patient and subsarcolemmal accumulation in seven patients. Strongly succinate dehydrogenase-reactive blood vessels (SSV) occurred in six patients. The molecular analysis of tRNA Leu(UUR) gene by PCR/RLFP and direct sequencing showed the A3243G mutation on mtDNA in 4 patients. CONCLUSION: The muscle biopsy often confirmed the MELAS diagnosis by presence of RRF and SSV. Molecular analysis of tRNA Leu(UUR) gene should not be the only diagnostic criteria for MELAS.

OBJETIVO: O objetivo deste estudo foi analisar uma série de pacientes brasileiros portadores de MELAS. MÉTODO: Dez pacientes com MELAS foram estudados com correlação entre manifestações clínicas, alterações laboratoriais, estudo eletrofisiológico, histoquímico e molecular. RESULTADOS: O nível de lactato sérico estava aumentado em 8 pacientes. O estudo das imagens do crânio revelou padrão semelhante ao de AVC isquêmico em todos os pacientes. A biópsia muscular mostrou fibras rajadas vermelhas (RRF) em 90 por cento dos pacientes na coloração pelo tricrômio de Gomori modificado e em 100 por cento na reação histoquímica pela desidrogenase succicínica (SDH). A análise da coloração pela citocromo c oxidase indicou atividade deficiente em um paciente e acúmulo subsarcolemal em sete pacientes. Vasos com forte reação para SDH (SSV) ocorreram em seis pacientes. O estudo molecular do gene tRNA Leu(UUR) por PCR/RLFP e seqüenciamento direto mostrou a mutação A3243G no DNAmt de 4 pacientes. CONCLUSÃO: A biópsia muscular frequentemente confirma o diagnóstico de MELAS pela presença de RRF e SSV. O estudo molecular do gene tRNA Leu(UUR) não deve ser o único critério diagnóstico para MELAS.

[Infantile encephalopathy associated with the MELAS A3243G mutation. Case report]. / Encefalopatía infantil asociada con la mutación A3243G MELAS.

Mitochondrial encephalopathies are a group of diseases that have as their pathogenic basis an alteration of the mitochondrial DNA (mtDNA). The MELAS phenotype (mitochondrial encephalomyopathy with lactic acidosis and stroke-like episodes) has been related to mutation A3243G in approximately 80% of the cases reported. MERRF (epilepsy myoclonus with ragged red fibers) has been related to mutation A8344G and A8566G of tRNA Lys. We report the case of a 7 months-old female with early clinical signs of encephalopathy associated to the A3243G mutation. Laboratory tests showed lactic acidosis and the EEG pattern was compatible with an encephalopathic process. The infant was treated with ACTH during one month, with clinical and electroencephalographic improvements. Currently, she is receiving treatment with B-vitamins, L-Carnitine and urinary alkalizing agents. It is concluded that an analysis of mtDNA must be made in infants who present convulsions, delay in their psychomotor development, lactic acidosis and an EEG pattern compatible with an encephalopathy, to rule out a mitochondrial disease.

Barth's syndrome-like disorder: a new phenotype with a maternally inherited A3243G substitution of mitochondrial DNA (MELAS mutation).

An Argentine male child died at 4.5 years of age of a lethal mitochondrial disease associated with a MELAS mutation and a Barth syndrome-like presentation. The child had severe failure to thrive from the early months and for approximately two years thereafter. In addition, the patient had severely delayed gross motor milestones, marked muscle weakness, and dilated cardiomyopathy that progressed to congestive heart failure. He also had persistently elevated urinary levels of 3-methylglutaconic and 2-ethylhydracrylic acids and low blood levels of cholesterol. Detailed histopathologic evaluation of the skeletal muscle biopsy showed high activity of succinate dehydrogenase, a generalized decrease of COX activity, and abundant ragged-red fibers. Electron microscopic studies revealed multiple mitochondrial abnormalities in lymphocytes and monocytes, in the striated muscle, and in the postmortem samples (muscle, heart, liver, and brain). Biochemical analysis showed a pronounced and constant lactic acidosis, and abnormal urinary organic acid excretion (unchanged in the fasting and postprandial states). In addition, in CSF there was a marked increase of lactate and beta-hydroxybutyrate (beta-HOB) and also a high systemic ratio beta-HOB/acetoacetate. Enzymatic assay of the respiratory chain in biopsied muscle showed 10% of complex I activity and 24% of complex IV activity compared with controls. Molecular studies of the mitochondrial genome revealed an A to G mutation at nucleotide pair 3243 in mitochondrial DNA, a well-known pathogenetic mutation (MELAS mutation) in all the patient's tissues and also in the blood specimens of the probands mother and sibs (4 of 5). The diagnosis of MELAS mutation was reinforced by the absence of an identifiable mutation in the X-linked G4.5 gene of the propositus. The present observation gives additional evidence of the variable clinical expression of mtDNA mutations in humans and demonstrates that all clinical variants deserve adequate investigation to establish a primary defect. It also suggests adding Barth-like syndrome to the list of phenotypes with the MELAS mutation.

Infantile encephalopathy associated with the MELAS A3243G mutation.

MELAS syndrome is typically characterized by normal early development and childhood-onset recurrent neurologic deficits (stroke-like episodes), seizures, short stature, lactic acidosis, and ragged red fibers on muscle biopsy specimens. It is usually, but not invariably, associated with the A3243G point mutation in the mitochondrial DNA tRNALeu(UUR) gene. We report 3 unrelated children with the A3243G mutation who presented with severe psychomotor delay in early infancy. One patient's clinical picture was more consistent with Leigh syndrome, with apneic episodes, ataxia, and bilateral striatal lesions on brain magnetic resonance imaging (MRI). The second patient had generalized seizures refractory to treatment and bilateral occipital lesions on brain MRI. The third child had atypical retinal pigmentary changes, seizures, areflexia, and cerebral atrophy on brain MRI. All patients had several atypical features in addition to early onset: absence of an acute or focal neurologic deficit, variable serum and cerebrospinal fluid lactate levels, lack of ragged red fibers in muscle biopsy specimens. The proportion of mutant mtDNA in available tissues was relatively low (range, 5% to 51% in muscle; 4% to 39% in blood). These observations further extend the phenotypic expression of the A3243G "MELAS" mutation. Our findings confirm previous observations that there is poor correlation between abundance of mutant mtDNA in peripheral tissues and neurologic phenotype. This suggests that other factors contribute to the phenotypic expression of this mutation.

Mal epilético como apresentaçäo de síndrome de Melas: relato de um caso / Status epilepticus as the presentation of Melas syndrome: a case report

É relatado e discutido o caso de uma paciente admitida no CTI devido a estado de mal epiléptico, atribuído a síndrome de Melas (miopatia mitocondrial, encefalopatia, acidose lática e episódios AVC-símile). A paciente era uma mulher jovem, com história pregressa de hopoacusia bilateral, crises episódicas de enxaqueca com vômitos, que apresentou-se em como, com sinais de irritaçäo meníngea e sem sinais de localizaçäo. Causas estruturais, infecciosas e auto-imunes foram afastadas através de exames laboratoriais e de imagem. Ao invés disso, demonstravam acidose lática grave, aumento de enzimas musculares, azotemia, hiperglicemia e leucocitose e presença de calcificaçöes dos gânglios da base e áreas isquêmicas na tomografia de crânio. Foi levantada a hipótese de Melas, a qual foi confirmada através de biópsia muscular que demonstrou fibras "ragged red" fortemente coradas pelo succinato desidrogenase (SDH). Os autores dirigem atençäo ao fato de uma síndrome rara também deve ser incluída no diagnóstico diferencial de um paciente jovem com convulsäo e acidose lática mesmo quando de uma apresentaçäo inicial.