High rate of hypertension in patients with m.3243A>G MELAS mutations and POLG variants.

Animal studies suggest that decreased vascular mitochondrial DNA copy number can promote hypertension. We conducted a chart review of blood pressure and hemodynamics in patients with either mitochondrial encephalopathy, lactic acidosis, and stroke-like episodes (MELAS, n = 36) or individuals with variants in the mitochondrial DNA polymerase gamma (POLG, n = 26). The latter included both pathogenic variants and variants of unknown significance (VUS). Hypertension rates (MELAS 50%, POLG 50%) were elevated relative to Canadian norms in 20-39 (MELAS) and 40-59 (MELAS and POLG) years of age groups. Peripheral resistance was high in the hypertensive versus normotensive patients, potentially indicative of microvascular disease. Despite antihypertensive treatment, systolic blood pressure remained elevated in the POLG versus MELAS group. The risk of hypertension was not associated with MELAS heteroplasmy. Hypertension rates were not different between individuals with known pathogenic POLG variants and those with VUS, including common variants. Hypertension (HT) also did not differ between patients with POLG variants with (n = 17) and without chronic progressive external opthalmoplegia (n = 9) (CPEO). HT was associated with variants in all three functional domains of POLG. These findings suggest that both pathogenic variants and several VUS in the POLG gene may promote human hypertension and extend our past reports that increased risk of HT is associated with MELAS.

Survival analysis of a cohort of Chinese patients with mitochondrial encephalomyopathy with lactic acidosis and stroke-like episodes (MELAS) based on clinical features.

BACKGROUND: Mitochondrial encephalomyopathy with lactic acidosis and stroke-like episodes (MELAS) is a common mitochondrial syndrome. The aim of this study was to conduct a survival analysis based on the clinical features of a Chinese MELAS patient cohort. METHODS: This is a retrospective single-center study. The MELAS patients were followed up for 1-8years (median 4years). The disease severity was evaluated by the modified Rankin Scale (mRS). The survival analysis was performed using Kaplan-Meier analysis and Cox proportional hazards model. RESULTS: A total of 138 subjects were enrolled, and the median disease duration was 7years [interquartile range (IQR) 4-11years]. The stroke-like episodes were the most common initial symptoms (70.3%). Seventeen (17.3%) subjects lost to follow-up. Of the 121 subjects who successfully completed the follow-up, 28 subjects died (mortality rate 23.1%). An acute stroke-like episode and/or status epilepticus were the predominant causes of death (42.9%). Among the surviving patients (n=93), 39.8% (37/93) required assistance in daily life (mRS scores 3-5). The mRS scores were inversely correlated with the age of onset (r=-0.28, P=0.0022) but not with the disease duration (r=0.10, P=0.2709). The survival rate declined mainly within 12years after the disease onset. The stroke-like episode as the initial symptom was an independent risk factor for death (hazard ratio=2.86, 95% CI 1.03-7.94, P=0.043). CONCLUSIONS: MELAS had high mortality and morbidity in this cohort of Chinese patients. The early onset of stroke-like episodes might indicate the more severe form of the disease, highlighting the importance of management of stroke-like episodes to improve the prognosis.

Frequency of MELAS main mutation in a phenotype-targeted young ischemic stroke patient population.

Mitochondrial diseases, predominantly mitochondrial encephalomyopathy, lactic acidosis, and stroke-like episodes (MELAS), may occasionally underlie or coincide with ischemic stroke (IS) in young and middle-aged individuals. We searched for undiagnosed patients with MELAS in a target subpopulation of unselected young IS patients enrolled in the Stroke in Young Fabry Patients study (sifap1). Among the 3291 IS patients aged 18-55 years recruited to the sifap1 study at 47 centers across 14 European countries, we identified potential MELAS patients with the following phenotypic features: (a) diagnosed cardiomyopathy or (b) presence of two of the three following findings: migraine, short stature (≤165 cm for males; ≤155 cm for females), and diabetes. Identified patients' blood samples underwent analysis of the common MELAS mutation, m.3243A>G in the MTTL1 gene of mitochondrial DNA. Clinical and cerebral MRI features of the mutation carriers were reviewed. We analyzed blood samples of 238 patients (177 with cardiomyopathy) leading to identification of four previously unrecognized MELAS main mutation carrier-patients. Their clinical and MRI characteristics were within the expectation for common IS patients except for severe hearing loss in one patient and hyperintensity of the pulvinar thalami on T1-weighted MRI in another one. Genetic testing for the m.3243A>G MELAS mutation in young patients with IS based on phenotypes suggestive of mitochondrial disease identifies previously unrecognized carriers of MELAS main mutation, but does not prove MELAS as the putative cause.

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)...

Detection rates and phenotypic spectrum of m.3243A>G in the MT-TL1 gene: a molecular diagnostic laboratory perspective.

The nucleotide change A to G at position m.3243 in the mitochondrial tRNA leucine (UUR) gene (MT-TL1) is the most common point mutation reported in association with the Mitochondrial Encephalomyopathy, Lactic Acidosis and Stroke-like episodes (MELAS) syndrome. Since the original description of this disorder, factors including random mitochondrial segregation and consequent variable tissue heteroplasmy are recognised to contribute to a much broader phenotypic spectrum associated with the MT-TL1 m.3243A>G mutation, often rendering the process of making a diagnosis complex. Reliance on clinicians' referral patterns means that for most molecular diagnostic laboratories, their positive identification rates for the common pathogenic mitochondrial DNA (mtDNA) mutations, including MT-TL1 m.3243A>G, is often relatively low compared to those reported in clinically targeted research studies. Herein, we report our results of consecutive prospective screening of 745 patients with a clinically suspected mitochondrial syndrome encompassing features associated with MT-TL1 m.3243A>G mutation.

The UK MRC Mitochondrial Disease Patient Cohort Study: clinical phenotypes associated with the m.3243A>G mutation--implications for diagnosis and management.

BACKGROUND: Population-based studies suggest the m.3243A>G mutation in MTTL1 is the most common disease-causing mtDNA mutation, with a carrier rate of 1 in 400 people. The m.3243A>G mutation is associated with several clinical syndromes including mitochondrial encephalopathy lactic acidosis and stroke-like episodes (MELAS), maternally inherited deafness and diabetes (MIDD) and progressive external ophthalmoplegia (PEO). Many patients affected by this mutation exhibit a clinical phenotype that does not fall within accepted criteria for the currently recognised classical mitochondrial syndromes. METHODS: We have defined the phenotypic spectrum associated with the m.3243A>G mtDNA mutation in 129 patients, from 83 unrelated families, recruited to the Mitochondrial Disease Patient Cohort Study UK. RESULTS: 10% of patients exhibited a classical MELAS phenotype, 30% had MIDD, 6% MELAS/MIDD, 2% MELAS/chronic PEO (CPEO) and 5% MIDD/CPEO overlap syndromes. 6% had PEO and other features of mitochondrial disease not consistent with another recognised syndrome. Isolated sensorineural hearing loss occurred in 3%. 28% of patients demonstrated a panoply of clinical features, which were not consistent with any of the classical syndromes associated with the m.3243A>G mutation. 9% of individuals harbouring the mutation were clinically asymptomatic. CONCLUSION: Following this study we propose guidelines for screening and for the management of confirmed cases.

Characteristics of intestinal pseudo-obstruction in patients with mitochondrial diseases.

AIM: To reveal the frequency, characteristics and prognosis of chronic intestinal pseudo-obstruction (CIP) in mitochondrial disease patients. METHODS: Between January 2000 and December 2010, 31 patients (13 males and 18 females) were diagnosed with mitochondrial diseases at our hospital. We conducted a retrospective review of the patients' sex, subclass of mitochondrial disease, age at onset of mitochondrial disease, frequency of CIP and the age at its onset, and the duration of survival. The age at onset or at the first diagnosis of the disorder that led to the clinical suspicion of mitochondrial disease was also examined. RESULTS: Twenty patients were sub-classified with mitochondrial encephalopathy with lactic acidosis and stroke-like episodes (MELAS), 8 with chronic progressive external ophthalmoplegia (CPEO), and 3 with myoclonus epilepsy associated with ragged-red fibers (MERRF). Nine patients were diagnosed with CIP, 8 of the 20 (40.0%) patients with MELAS, 0 of the 8 (0.0%) patients with CPEO, and 1 of the 3 (33.3%) patients with MERRF. The median age (range) at the diagnosis and the median age at onset of mitochondrial disease were 40 (17-69) and 25 (12-63) years in patients with CIP, and 49 (17-81) and 40 (11-71) years in patients without CIP. During the survey period, 5 patients (4 patients with MELAS and 1 with CPEO) died. The cause of death was cardiomyopathy in 2 patients with MELAS, cerebral infarction in 1 patient with MELAS, epilepsy and aspiration pneumonia in 1 patient with MELAS, and multiple metastases from gastric cancer and aspiration pneumonia in 1 patient with CPEO. CONCLUSION: Patients with CIP tend to have disorders that are suspected to be related to mitochondrial diseases at younger ages than are patients without CIP.

MELAS: a nationwide prospective cohort study of 96 patients in Japan.

BACKGROUND: MELAS (mitochondrial myopathy, encephalopathy, lactic acidosis and stroke-like episodes) (OMIM 540000) is the most dominant subtype of mitochondrial myopathy. The aim of this study was to determine the prevalence, natural course, and severity of MELAS. METHODS: A prospective cohort study of 96 Japanese patients with MELAS was followed between June 2003 and April 2008. Patients with MELAS were identified and enrolled based on questionnaires administered to neurologists in Japan. MELAS was defined using the Japanese diagnostic criteria for MELAS. Two follow-up questionnaires were administered to neurologists managing MELAS patients at an interval of 5years. RESULTS: A prevalence of at least 0.58 (95% confidential interval (CI), 0.54-0.62)/100,000 was calculated for mitochondrial myopathy, whereas the prevalence of MELAS was 0.18 (95%CI, 0.02-0.34)/100,000 in the total population. MELAS patients were divided into two sub-groups: juvenile form and adult form. Stroke-like episodes, seizure and headache were the most frequent symptoms seen in both forms of MELAS. Short stature was significantly more frequent in the juvenile form, whereas hearing loss, cortical blindness and diabetes mellitus were significantly more frequent in the adult form. According to the Japanese mitochondrial disease rating scale, MELAS patients showed rapidly increasing scores (mean±standard deviation, 12.8±8.7) within 5years from onset of the disease. According to a Kaplan-Meier analysis, the juvenile form was associated with a higher risk of death than the adult form (hazard ratio, 3.29; 95%CI, 1.32-8.20; p=0.0105). CONCLUSIONS AND GENERAL SIGNIFICANCE: We confirmed that MELAS shows a rapid degenerative progression within a 5-year interval and that this occurs in both the juvenile and the adult forms of MELAS and follows different natural courses. This article is part of a Special Issue entitled: Biochemistry of Mitochondria.

Value of brain magnetic resonance imaging in mitochondrial respiratory chain disorders.

Mitochondrial respiratory chain (MRC) disorders have variable clinical manifestations which are mainly neurologic. Diagnosis in children is more complex than in adults because the classic phenotype, ragged red fibers, and mtDNA mutations are rarely seen in children. Moreover, clinical manifestations of disease in developing brains are less explicit. Although not specific, neuroimaging may be contributory to the diagnosis of these disorders in pediatric patients. Brain magnetic resonance images were reviewed for 133 pediatric patients investigated for a MRC disorder at a single center over a period of 10 years (1997-2006), in an attempt to identify distinctive neuroimaging features of MRC defects. Patients fit into four groups, according to the Bernier criteria: definite (63 cases), probable (53 cases), possible (7 cases) and unlikely diagnosis (10 cases). Brain atrophy (41 cases), supratentorial white matter lesions (14 cases), basal ganglia involvement (9 cases), and delayed myelination (9 cases) were the most frequent anomalies in the definite group, and 8 patients presented Leigh syndrome. Neuroimaging findings of the 63 children in the definite group were compared with the remainder and with those in the possible and unlikely groups. There were no significant differences in brain images between the groups analyzed, and therefore no distinctive brain imaging features were identified specific for MRC disorders.

Migraine and ischemic stroke: a debated question.

Numerous epidemiologic observations reporting high prevalence of migraine among young individuals with stroke as well as dysfunction of cerebral arteries during migraine attacks prompt speculation on the existence of a comorbidity between the two disorders. The recent finding of silent infarct-like brain lesions in migraineurs reinforced this hypothesis and raised questions on whether migraine may be a progressive disorder rather than simply an episodic disorder. Stroke can occur during the course of migraine attacks with aura, supporting the assumption of a causal relation between the two diseases. Migraine may accentuate other existing risk factors for stroke, and both jointly increase the risk of cerebral ischemia outside of migraine attacks. In this regard, the role of migraine might be that of predisposing condition for cerebral ischemia. Migraine and ischemic stroke may be the end phenotype of common pathogenic mechanisms. Evidence of a migraine-stroke relation in cases of specific disorders, such as CADASIL (cerebral autosomal-dominant arteriopathy with subcortical infarcts and leukoencephalopathy) and MELAS (mitochondrial myopathy, encephalopathy, lactic acidosis, and stroke-like episodes), strongly supports this concept. Finally, acute focal cerebral ischemia can trigger migraine attacks, and, thus, migraine may be the consequence of stroke. In this paper, we will review contemporary epidemiologic studies, discuss potential mechanisms of migraine-induced stroke and comorbid ischemic stroke, and pose new research questions.

Muscle physiology in healthy men and women and those with metabolic myopathies.

The relative contribution and source of the fuels used during endurance exercise is dependent on the intensity and the duration of the exercise. Much work has been done to investigate the potential performance-enhancing effect of manipulating training and dietary interventions in athletes, as well as the influence of gender. Studies show that even patients with metabolic myopathies may derive benefits that counter the age-associated loss of muscle mass and strength. This article gives an overview of these different impacts on endurance exercise, concluding with an examination of the metabolic myopathies that impair substrate metabolism in skeletal muscle and result in exercise intolerance.

[L-arginine therapy on MELAS].

MELAS is the most dominant clinical features among mitochondrial disorders. However the natural course of MELAS has not been clarified yet. In order to elucidate the natural course of MELAS, we have done the Japanese Cohort study on MELAS. By the age of onset, we divided MELAS into two subgroups, a juvenile form (onset is less than 18 years of age) and an adult form (onset is more than 18 years of age). Juvenile form is significantly different from adult form not only in the mean age of onset, but the mean age of death and survival rate (juvenile has 3.2 times higher chance of death than adult). Our date indicate that juvenile form of MELAS is more severe and poor prognosis than those seen in adult form. Based on the hypothesis that MELAS is caused by impaired vasodilation in an intracerebral artery, we evaluated the effects of administering L-arginine, a nitric oxide precursor. Patients were administered L-arginine intravenously at acute phase, or per orally at interictal phase. L-arginine infusions significantly improved all stroke-like symptoms suggesting stroke within 30 min, and oral administration significantly decreased frequency and severity of stroke-like episodes. L-arginine therapy showed promise in treating stroke-like episodes in MELAS.

Population prevalence of the MELAS A3243G mutation.

We aimed to establish the population prevalence of the MELAS 3243A>G mtDNA mutation in a large Caucasian-based population (n=2954; 99% Caucasian, 57% women and mean age of 66.4 years). All participants underwent comprehensive clinical evaluation including audiologic testing. We detected the 3243A>G mutation in seven subjects using standard polymerase chain reaction/restriction fragment length polymorphism methods, establishing a population prevalence of 236/100000 (0.24%; 95% CI 0.10-0.49%); much higher than previously reported. All had mild to moderate hearing loss. Our findings indicate that subjects with the 3243A>G mtDNA mutation could be markedly under-recognised in the community.

Mitochondrial encephalopathy with lactic acidosis and stroke-like episodes syndrome with hypothyroidism and focal segmental glomerulosclerosis in a paediatric patient.

Herein, we report on a paediatric patient with mitochondrial encephalopathy, lactic acidosis and stroke-like episodes (MELAS) who was hospitalized for acute on chronic renal insufficiency, seizures and deterioration of the level of consciousness. She also had hypertension, hypothyroidism and nephrotic range proteinuria. Kidney biopsy revealed many sclerotic glomeruli and focal segmental glomerulosclerosis (FSGS). Glomerulopathy is rare in patients with MELAS, and FSGS has been reported only in a few patients. The histopathological features of the renal biopsy suggested that the aetiology of the FSGS may have been secondary to chronic renal injury rather than from a primary immunologic cause. Moreover, our case is unique in that, the coexistence of MELAS, hypothalamic hypothyroidism and FSGS has not been reported in the past. The purpose of this report is to increase the awareness of health-care professionals, especially in the fields of paediatrics, neurology, endocrinology and nephrology, regarding the manifestations and complications of MELAS.

Clinical features of A3243G mitochondrial tRNA mutation.

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.

Prevalence and progression of mitochondrial diseases: a study of 50 patients.

We report 50 patients with various clinical phenotypes of mitochondrial disease studied over the past 10 years in a large urban area (Madrid Health Area 5). The clinical phenotypes showed a large variety of abnormalities in molecular biology and biochemistry. The prevalence of mitochondrial diseases was found to be 5.7 per 100,000 in the population over 14 years of age. Clinical and electrophysiological assessment reveal signs of neuropathy in 10 patients. Electromyographic findings consistent with myopathy were obtained in 37 cases. Six patients died of medical complications. Disease phenotype influenced survival to some degree (P < 0.01). Age of onset and gender were not associated with differences in survival. Mitochondrial disease is thus far more common than expected and a common cause of chronic morbidity.

Childhood encephalopathies and myopathies: a prospective study in a defined population to assess the frequency of mitochondrial disorders.

OBJECTIVES: To assess the frequency of mitochondrial abnormalities in muscle histology, defects in respiratory chain enzyme activities, and mutations in mitochondrial DNA (mtDNA) in children with unexplained psychomotor retardation in the population of Northern Finland. BACKGROUND: The frequency of mitochondrial diseases among patients with childhood encephalopathies and myopathies is not known. Frequencies are difficult to estimate because the clinical presentation of these disorders is variable. METHODS: A total of 116 consecutive patients with undefined encephalopathies and myopathies were enrolled during a 7-year period in a hospital serving as the only neurologic unit for a pediatric population of 97 609 and as the only tertiary level neurologic unit for a pediatric population of 48 873. Biochemical and morphologic investigations were performed on muscle biopsy material, including oximetric and spectrophotometric analyses of oxidative phosphorylation, histochemistry, electron microscopy, and molecular analysis of mtDNA. RESULTS: Ultrastructural changes in the mitochondria were the most common finding in the muscle biopsies (71%). Ragged-red fibers were found in 4 cases. An oxidative phosphorylation defect was found in 26 children (28%), complex I (n = 15) and complex IV (n = 13) defects being the most common. Fifteen percent of patients (n = 17/116) with unexplained encephalomyopathy or myopathy had a probable mitochondrial disease. Common pathogenic mutations were found in the mtDNA of only 1 patient (.9%). CONCLUSIONS: The common known mutations in mtDNA are rarely causes of childhood encephalomyopathies, which is in contrast to the considerable frequency of the common MELAS mutation observed among adults in the same geographical area. Biochemically and morphologically verified mitochondrial disorders were nevertheless common among the children, making the analysis of a muscle biopsy very important for clinical diagnostic purposes.

Increased prevalence of vitiligo, but no evidence of premature ageing, in the skin of patients with bp 3243 mutation in mitochondrial DNA in the mitochondrial encephalomyopathy, lactic acidosis and stroke-like episodes syndrome (MELAS).

The MELAS syndrome (mitochondrial encephalomyopathy, lactic acidosis and stroke-like episodes) belongs to the category of mitochondrial disorders. The most common molecular aetiology of the syndrome is a mutation at base pair (bp) 3243 in the mitochondrial genome (mtDNA). The phenotype is varied and, apart from central nervous system involvement, the patients with this mutation may present with neurosensory hearing loss, diabetes mellitus and cardiomyopathy. These phenotypes suggest that organs dependent on aerobic metabolism suffer most. We investigated the possible clinical and physiological manifestations of impaired energy metabolism in the skin of 28 patients with the bp 3243 mutation in mtDNA. Non-invasive sonography and laser Doppler flowmetry were used to measure skin thickness and the blood flow of the skin. Skin collagen synthesis was assayed from suction blister fluid. Evaporimetry was used to assess the re-epithelialization rate of suction blister wounds. Histochemistry and immunohistochemistry were used to evaluate the melanocytes and pigment in the skin. Vitiligo was found in three of the 28 patients (11%), which was markedly more than in the general population. Histological findings showed an absence of pigment, but an apparently normal distribution of melanocytes in the dermoepidermal junction. Seborrhoeic eczema and atopy were also somewhat more frequent. No features of premature ageing, such as a marked decrease in skin thickness, blood flow, collagen synthesis or re-epithelialization rate, were demonstrated.