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

In recent years, several point mutations in the mitochondrial genome have been associated with human disease. PCR Polymerase Chain Reaction/restriction endonuclease based techniques provide a reliable method for screening large numbers of specimens for many of the reported mutations. Muscle tissue usually carries the mutations and has been used in earlier studies. We describe a technique for analysis of mtDNA derived from hair follicles for a range of mutations. Both the 3243 A-->G MELAS and 8344 A-->G MERRF mutations were detected in mtDNA from hair follicles. In patients where both muscle and hair were screened, the mutation load was apparently higher in muscle. Furthermore, in patients positive for a given mutation, all the hair follicles analysed were shown to harbour the mutation, although the proportion of wild type to mutant mtDNA was found to somewhat vary. The advantages of this method are (1: six hair follicles provide sufficient mtDNA for analysis of at least 20 different mutations, and (2: specimen collection and transport to a central laboratory are easier than for other tissues. Our studies show that hair follicles constitute a reliable specimen for mitochondrial mutation screening at a diagnostic level.
 ...
PMID:Rapid and noninvasive screening of patients with mitochondrial myopathy. 798 17

Polymerase chain reaction (PCR) based methods for the diagnosis and screening of the mitochondrial disorders have been well established. A number of tissues are routinely used. In this study, we compared the detection rate for MELAS A3243G point mutation in muscle, blood and hair follicles. Ten subjects were studied; mean age was 47 years, (SD 16, range 23-73). All ten subjects had the MELAS A3243G point mutation detected in muscle and hair follicles, but only five had the abnormality in blood samples. The rate of detection of the point mutation in blood samples was age dependent. MtDNA analysis on hair follicles is as sensitive as muscle in detecting this mutation. Analysis using blood samples is not as sensitive, particularly in older subjects. The absence of the mutation in blood samples suggests that there is a preferential selection process for normal (wild type) mtDNA over time. This may be related to the rate of cell division and energy requirements of each tissue.
 ...
PMID:Detection of MELAS A3243G point mutation in muscle, blood and hair follicles. 987 79

Mitochondrial encephalopathy, lactic acidosis with stroke-like episodes (MELAS) is a rare mitochondrial disorder that affects adults. MELAS syndrome can mimic cerebrovascular disease, encephalitis or toxic-metabolic encephalopathy. The authors reported two patients who presented with auditory symptoms before the onset of encephalopathy and stroke-like episodes. The first patient was a 28 year-old man, who presented with acute sensorineural hearing loss (SNHL) followed by headache, left hemiparesis and generalized tonic-clonic seizure. CT scan of the brain showed hypodensity lesion at the tip of right temporooccipital region. Audiogram and brainstem auditory evoked potential (BAEP) showed abnormal conduction of left brainstem auditory pathway. MRI of the brain showed a lesion involving gray and white matters of the right occipital, parietal and temporal lobes. The distribution of the lesions was not compatible with distribution of arterial supply. MRA was normal. The second patient was a 56 year-old woman with a one-year history of hearing loss. The audiogram revealed bilateral SNHL. A few days before admission, her hearing was acutely deteriorated She could not understand a conversation while she could communicate by writing. CT scan of the brain showed hypodensity in both temporal lobes and MRI revealed lesions in the same area. Pure tone audiogram showed moderate SNHL but BAEP was normal. One week later, she developed global dysphasia and generalized tonic-clonic seizure. Both patients had elevated cerebrospinal fluid and serum lactate: pyruvate ratio. Polymerase chain reaction-restriction fragment length polymorphism disclosed A3243G mtDNA mutation in the blood in the first patient and in muscle biopsy in the second patient. Ubiquinone supplement was prescribed The auditory symptoms in combination with stroke-like episode in supratentorium are important clues to diagnose MELAS syndrome.
 ...
PMID:Auditory symptoms: a critical clue for diagnosis of MELAS. 1647 Nov 25

Mitochondrial DNA (mtDNA) disease is an important genetic cause of neurological disability. A variety of different clinical features are observed and one of the most common phenotypes is MELAS (Mitochondrial Myopathy, Encephalopathy, Lactic Acidosis and Stroke-like episodes). The majority of patients with MELAS have the 3243A>G mtDNA mutation. The neuropathology is dominated by multifocal infarct-like lesions in the posterior cortex, thought to underlie the stroke-like episodes seen in patients. To investigate the relationship between mtDNA mutation load, mitochondrial dysfunction and neuropathological features in MELAS, we studied individual neurones from several brain regions of two individuals with the 3243A>G mutation using dual cytochrome c oxidase (COX) and succinate dehydrogenase (SDH) histochemistry, and Polymerase Chain Reaction Restriction Fragment Lenght Polymorphism (PCR-RFLP) analysis. We found a low number of COX-deficient neurones in all brain regions. There appeared to be no correlation between the threshold level for the 3243A>G mutation to cause COX deficiency within single neurones and the degree of pathology in affected brain regions. The most severe COX deficiency associated with the highest proportion of mutated mtDNA was present in the walls of the leptomeningeal and cortical blood vessels in all brain regions. We conclude that vascular mitochondrial dysfunction is important in the pathogenesis of the stroke-like episodes in MELAS patients. As migraine is a commonly encountered feature in MELAS, we propose that coupling of the vascular mitochondrial dysfunction with cortical spreading depression (CSD) might underlie the selective distribution of ischaemic lesions in the posterior cortex in these patients.
 ...
PMID:Molecular neuropathology of MELAS: level of heteroplasmy in individual neurones and evidence of extensive vascular involvement. 1686 82