Point mutations of muscle mitochondrial DNA from patients with mitochondrial encephalomyopathies

Objective To study the relation between point mutations at nt3243 and nt8344 of muscle mitochondrial DNA from patients with mitochondrial encephalomyopathies and phenotypes. Methods DNA was extracted from muscle specimens from 5 patients with mitochondrial encephalomyopathies and amplified by PCR method, using corresponding oligonucleotide primers. DNA fragments were digested with restriction enzymes BglⅠ and ApaⅠ, then the digested DNA fragments were analyzed with an electrophoresis method.Results The point mutation at nt3243 of mtDNA was found in 2 patients, one with mitochondrial encephalomyopathy, lactic acidosis and stroke-like episodes (MELAS) and another with myoclonic epilepsy with ragged red fibers (MERRF). The point mutation at nt8344 was found in 2 patients with MERRF, including the one with point mutation at nt3243.Conclusion The point mutation of DNA at nt3243 correlated with MELAS and nt8344 correlated with MERRF. In addition, the detection of point mutations at both nt3243 and nt8344 in a patient with MERRF shows the association of mutation with diversity in clinical manifestations of mitochondrial encephalomyopathies.

EVALUATION OF MITOCHONDRIAL ENCEPHALOMYOPATHY WITH LACTIC ACIDOSIS AND STROKE-LIKE EPISODES WITH MAGNETIC RESONANCE IMAGING AND PROTON MAGNETIC RESONANCE SPECTROSCOPY

Objective To study the characteristics of spectra on proton magnetic resonance spectroscopy （^1H-MRS） and its value in patients with mitochondrial encephalomyopathy with lactic acidosis and stroke-like episodes （MELAS）. Methods Seven clinically diagnosed patients with MELAS underwent magnetic resonance imaging （MRI） and ^1H-MRS examinations. The ^1H-MRS techniques, characteristics of the spectra, and its correlation with the laboratory tests were analyzed. Reaults Cerebral abnormalities were revealed in all 7 patients on conventional MR images, and most abnormal signals were observed in bilateral occipital, parietal, and temporal lobes. We found 4 cases with basal ganglia involvement, 2 cases with mild frontal lobe lesions, and 1 case with involvement of lateral cerebral peduncles and thalami. Additionally, 1 patient was involved with left insular lobe. Spectra from prominent lesions in brain parenchyma showed lactate doublet peak in 6 patients, 3 of whom were also noted lactate peak in ventricular cerehrospinal fluid （CSF）. Conclusion ^1H-MRS may provide more direct information about the metabolism changes, which aids to affirm the diagnosis, and may replace the conventional invasive method of quantifying lactate in CSF.

Familial mitochondrial encephalomyopathy,lactic acidosis,and stroke-like episode syndrome:Three case reports

BACKGROUND Mitochondrial encephalomyopathy(ME)is a multisystem metabolic disease that primarily affects the central nervous system and skeletal muscle.It is caused by mutations in mitochondrial or nuclear DNA,resulting in abnormal mitochondrial structure and function and insufficient ATP synthesis.The most common subtype is mitochondrial encephalomyopathy,lactic acidosis,and stroke-like episode(MELAS)syndrome.In recent years,reports of MELAS syndrome have increased but familial cases are rare.CASE SUMMARY We report a case of familial MELAS syndrome.Cases 2 and 3 are sisters and case 1 is their nephew.All are short in stature and showed stroke-like episodes with rapid onset and no obvious symptoms such as paroxysmal headache,aphasia,or blurred vision.After admission,blood lactate levels were significantly higher than normal.The patients underwent magnetic resonance imaging of the head.Cases 1 and 2 were considered to have ME,whereas case 3 was considered to have a space-occupying lesion in the left temporal lobe.Pathological evaluation showed no obvious tumor cells in the brain lesions of case 3.Muscle biopsy or genetic test results were consistent with ME.The patients were diagnosed with MELAS syndrome and their symptoms improved with intravenous infusions of coenzyme Q10,coenzyme A,vitamin B,and vitamin C.At the 6 mo follow-up,there was no recurrence or progression.CONCLUSION When a patient has MELAS syndrome,familial MELAS syndrome should be considered if related family members have similar symptoms.

Myopathological features in MELAS syndrome without significant changes in muscle biopsy pathology

Mitochondrial encephalomyopathy, lactic acidosis, and stroke-like episodes （MELAS） are common types of mitochondrial encephalomyopathy. The involved muscular pathology is characterized by typical changes of mitochondrial abnormalities. Gene screening has been the gold diagnostic standard for MELAS diagnosis. This study presents three primary MELAS patients, with an age of onset from 13 to 18 years, including one patient with seizure, and two with headache and vomiting. All patients had a family history of disease, with maternal inheritance. Cerebral magnetic resonance imaging revealed abnormally high signals in T2-weighted images： temporal lobe in three cases, occipital lobe in two cases, and parietal lobe in one case. Migrating stroke-like lesions were confirmed in one patient. Muscle biopsy revealed several strongly succinate dehydrogenase-reactive vessels scattered in muscle sections of three patients, but ragged-red fibers and cytochrome c oxidase-negative/dense （COX-/＋） fibers were not observed. Mitochondrial DNA A3243G mutation was identified in all three cases. MELAS syndrome has obvious clinical heterogeneity, and muscle weakness was not prominent in some of the cases. Muscle pathological changes did not accompany ragged-red fibers or COX-/＋ fibers, but succinate dehydrogenase- reactive vessels are important for MELAS diagnosis.

Detection of A3243G point mutation in mitochondrial DNA from 10 cases of MELAS

Objective To search for A3243G point mutations in mitochondrial DNA (mtDNA) from 10 cases of mitochondrial encephalomyopathy, lactic acidosis and strokelike episodes (MELAS) Methods Using PCR restriction analysis, we investigated A3243G point mutations in mtDNA of muscle and/or blood cells from 10 patients and their 8 maternal relatives We also quantitated the A3243G mtDNA in samples harboring the mutation Results A3243G point mutations were identified in all muscle and/or blood samples from 10 MELAS patients The proportion of mutant mtDNA was 10 8%-47 8% in blood (7 cases), and 39 4%-67 7% in muscle (5 cases) This ratio was invariably higher in muscle than in blood from two patients whose blood and muscle samples were both available Younger patients usually carried higher proportions of A3243G mutant mtDNA in blood Eight maternal relatives from 6 families were also examined Maternal transmission of the disease could be identified in one family No A3243G point mutations were found in mothers' blood from 3 families and siblings' blood from 2 families Conclusions All 10 MELAS patients were found to have the mtDNA A3243G mutation in their muscle and/or blood The A3243G mutation seems to be sporadic in 5 of the families examined, suggesting the mechanism of de novo mutation for the pathogenesis of their MELAS syndrome

Clinical,pathological and genetic study of a kindred of mitochondrial encephalomyopathy with lactic acidosis and stroke-like episodes

The first description of a syndrome including stroke-like episodes, lactic acidaemia, and ragged red fibres, was reported by Shapira et al in 1975. 1 Pavlakis et al 2 described further cases, introduced the acronym MELAS (mitochondrial encephalomyopathy with lactic acidosis and stroke-like episodes), and suggested that this represented a distinct mitochondrial disease phenotype. In 1990, Goto et al 3 identified A3243G mutation in the transfer RNA (tRNA) leucine (UUR) gene in some patients with MELAS. Although this mutation has now been established to be the commonest mtDNA defect it is often misdiagnosed. Here we report a kindred of MELAS including a mother and a son. Clinical, pathological and genetic studies are proceeding.