ABSTRACT
OBJECTIVES: To evaluate three patients with the mitochondrial encephalopathy, lactic acidosis and cerebrovascular accident syndrome (MELAS) diagnosed in childhood, with particular reference to the initial symptoms and clinical evolution during the first stage at a pediatric age, and to compare them with other studies on the subject. PATIENTS AND METHODS: Two boys and a girl of 10, 11 and 13 years had tests on lactate, pyruvate and aminoacids in biological fluids under basal conditions and also functional tests and enzyme activity assay of the mitochondrial respiratory chain of a muscle biopsy. We also analysed the particular DNA mutations related to MELAS in different tissues from these patients and in lymphocytes from members of the mothers' families who could be tested. RESULTS: The patients fulfilled the clinical criteria for the MELAS syndrome. Neuroimaging showed cerebrovascular accidents. Neurophysiological studies showed myopathy in one patient and neuroaxonal neuropathy in another. In two cases ophthalmological study showed retinitis pigmentaria and during cerebrovascular accidents transient phenomena of homonymous hemianopsia and cortical blindness were seen. In all patients muscle biopsy showed ragged red fibres and the biochemical study showed an enzyme deficit in the respiratory mitochondrial chain. On molecular genetic study of the mitochondrial DNA (mtDNA) there was a particular mutation A3243G on the tRNA(Leu) in all patients and some members of the mothers' families. CONCLUSIONS: In children with frequent episodes of migraine headaches, vomiting, refractory epilepsy and fatigue the presence of a mitochondrial disease should be suspected. On detection of mtDNA mutations MELAS may be diagnosed even without all the clinical criteria which characterise this syndrome.
Subject(s)
DNA, Mitochondrial/genetics , MELAS Syndrome/genetics , Mutation/genetics , RNA, Transfer, Leu/genetics , Child , Female , Humans , MELAS Syndrome/diagnostic imaging , Magnetic Resonance Imaging , Male , Pedigree , Tomography, X-Ray ComputedABSTRACT
OBJECTIVES: To evaluate the results of oxygen consumption measurement in lymphocytes for the diagnosis and treatment monitoring of pediatric patients with oxidative phosphorylation diseases. DESIGN AND METHODS: Twenty-four children with an oxidative phosphorylation disease were studied. Results were compared with those of 87 healthy children. Oxygen consumption measurements in digitonine-permeabilized lymphocytes incubated with pyruvate plus malate and succinate were performed in a Clark-type oxygen electrode. RESULTS: A total of 58% of patients showed a decreased oxygen consumption in lymphocytes incubated with pyruvate. In 4 patients, this analysis was the unique initial biochemical test, which revealed an impaired mitochondrial energy metabolism. Significant differences were observed in lymphocytes incubated with pyruvate between patients and reference values (p<0.00005), and in lymphocytes incubated with pyruvate before and after treatment (p<0.05). CONCLUSIONS: This test is useful for diagnosing oxidative phosphorylation diseases in patients who did not have other biochemical alterations, although false-negative results can be found. It is not useful for treatment monitoring.
Subject(s)
Lymphocytes/metabolism , Metabolic Diseases/diagnosis , Oxidative Phosphorylation , Oxygen Consumption/physiology , Adolescent , Child , Child, Preschool , DNA, Mitochondrial/analysis , Digitonin/pharmacology , Electron Transport , Energy Metabolism/physiology , Female , Humans , Indicators and Reagents/pharmacology , Infant , Lymphocytes/chemistry , Lymphocytes/drug effects , Malates/pharmacology , Male , Metabolic Diseases/genetics , Metabolic Diseases/metabolism , Mitochondria/enzymology , Mitochondria/metabolism , Polarography , Pyruvic Acid/pharmacology , Reference Values , Succinic Acid/pharmacologyABSTRACT
INTRODUCTION: Human diseases caused by disorders of the mitochondrial metabolism have been described more than 30 years ago. Some of these are associated to defects in the oxidative phosphorylation system (OXPHOS system), the final pathway of the mitochondrial energetic metabolism, that leads to the synthesis of ATP. DEVELOPMENT: Part of the polypeptide subunits involved in the OXPHOS system are codified by the mitochondrial DNA (mtDNA). In the last 12 years, mutations (point mutations or deletions) in the mtDNA have been described and associated to well defined clinical syndromes caused by defects in the OXPHOS system. The clinical features of these diseases are very heterogeneous affecting in most cases to a great variety of organs and tissues. CONCLUSIONS: The correct diagnosis of these mitochondrial disorders require precise clinical, morphological, biochemical, and genetic data. The rapid advances in genetic analysis allow the rapid detection of mutations, even before the obtention of other type of analysis.
Subject(s)
DNA, Mitochondrial/metabolism , Mitochondrial Myopathies/metabolism , DNA Mutational Analysis , DNA, Mitochondrial/classification , DNA, Mitochondrial/genetics , Gene Expression/genetics , Humans , Mitochondrial Myopathies/genetics , Oxidative Phosphorylation , Point Mutation/geneticsABSTRACT
Introducción. Desde hace más de 30 años se conocen diversas anomalías del metabolismo mitocondrial que producen enfermedades humanas. Entre ellas se encuentran los defectos en el sistema de fosforilación oxidativa (sistema OXPHOS), la ruta final del metabolismo energético mitocondrial que conduce a la síntesis de ATP. Desarrollo. Este sistema presenta la particularidad de que una parte de las subunidades proteicas que lo componen están codificadas en el ADN mitocondrial. En los últimos 12 años se han descrito una serie de mutaciones (puntuales o deleciones) en el ADN mitocondrial que se han asociado con síndromes clínicos bien definidos originados por defectos en el sistema OXPHOS. Los caracteres clínicos de estas enfermedades son muy heterogéneos y, excepto en algún caso, afectan a gran variedad de órganos y tejidos. Conclusiones. El diagnóstico preciso de este grupo de trastornos requiere la obtención de datos clínicos, morfológicos, bioquímicos y genéticos. La utilización de técnicas sencillas de genética molecular permite la detección rápida de mutaciones, incluso antes de que puedan realizarse otros tipos de análisis (AU)
Subject(s)
Middle Aged , Male , Humans , Mesencephalon , Saccades , Tomography, X-Ray Computed , Gene Expression , Point Mutation , Mitochondrial Myopathies , Oxidative Phosphorylation , Ophthalmoplegia , Cerebral Hemorrhage , DNA, Mitochondrial , DNA Mutational Analysis , Magnetic Resonance ImagingABSTRACT
INTRODUCTION: Recently the molecular basis of a series of clinical disorders associated with defects in the oxidative phosphorylation system (OXPHOS system) leading to ATP synthesis, the final pathway of mitochondrial energy metabolism, has been established. The polypeptide components of the OXPHOS system are codified in both nuclear and mitochondrial DNA. Therefore these mitochondrial diseases may be originated by mutations of genes found in both genetic systems. DEVELOPMENT: In recent years, several such neuromuscular diseases have been defined and associated with mitochondrial DNA mutations. One of the most striking of these is the syndrome of myoclonic epilepsy with ragged red fibres (MERRF), characterized by myoclonic epilepsy of maternal inheritance. This disorder is caused by a specific mutation on the mitochondrial tRNA(Lys) (position 8344), which gives rise to a reduction in the level of lysil-tRNA(Lys) and thus to premature termination of the translation of proteins codified in the mitochondrial DNA.
