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

Black Toenail Sign in MELAS Syndrome

BACKGROUND

Mitochondrial encephalopathy with lactic acidosis and stroke-like episodes (MELAS) syndrome is a mitochondrial disorder often causing progressive brain injury that is not confined to large arterial territories. Severe insults ultimately lead to gyral necrosis affecting the cortex and juxtacortical white matter; the neuroimaging correlate is partial gyral signal suppression on T2/FLAIR sequences that resemble black toenails. We aimed to characterize the imaging features and the natural history of MELAS-related gyral necrosis.

MATERIALS AND METHODS

Databases at two children's hospitals were searched for brain magnetic resonance imaging studies of individuals with MELAS. Examinations with motion artifact and those lacking T2/FLAIR sequences were excluded. The location, the cumulative number, and the maximum transverse diameter of necrotic gyral lesions were assessed using T2-weighted images and T2/FLAIR sequences. Wilcoxon signed-rank test was employed to evaluate the relationship between disease duration and the number of necrotic lesions.

RESULTS

One hundred twenty-four examinations from patients with 14 unique MELAS patients (16 ± 3 years) were evaluated. Six of the eight patients who developed brain lesions also developed gyral necroses (mean 13, range 0 to 44). Necrotic lesions varied in maximal diameter from 4 to 25 mm. Cumulative necrotic lesions correlated with disease duration (P < 0.001).

CONCLUSIONS

The black toenail sign signifying gyral necrosis is a common imaging feature in individuals with MELAS syndrome. The extent of gyral necrosis correlates with disease duration.

Genetics of Mitochondrial Disease

Mitochondria are intracellular organelles responsible for adenosine triphosphate production. The strict control of intracellular energy needs require proper mitochondrial functioning. The mitochondria are under dual controls of mitochondrial DNA (mtDNA) and nuclear DNA (nDNA). Mitochondrial dysfunction can arise from changes in either mtDNA or nDNA genes regulating function. There are an estimated ∼1500 proteins in the mitoproteome, whereas the mtDNA genome has 37 proteins. There are, to date, ∼275 genes shown to give rise to disease. The unique physiology of mitochondrial functioning contributes to diverse gene expression. The onset and range of phenotypic expression of disease is diverse, with onset from neonatal to seventh decade of life. The range of dysfunction is heterogeneous, ranging from single organ to multisystem involvement. The complexity of disease expression has severely limited gene discovery. Combining phenotypes with improvements in gene sequencing strategies are improving the diagnosis process. This chapter focuses on the interplay of the unique physiology and gene discovery in the current knowledge of genetically derived mitochondrial disease.

Late onset MELAS with m.3243A > G mutation and its association with aneurysm formation

We reported a 53-year-old with late-onset mitochondrial encephalomyopathy, lactic acidosis, and stroke-like episodes (MELAS) accompanied by aneurysm and large vessel dilations. Most studies have focused on microangiopathy causing stroke-like episodes. We report a case to describe large vessel involvement in clinical considerations, and possible mechanisms of aneurysm formation. We recommended regular angiographic examination for patients with MELAS.

Importance of Distinguishing Between Mitochondrial Encephalomyopathy With Elderly Onset of Stroke-Like Episodes and Cerebral Infarction

The most common disease-causing mitochondrial DNA (mtDNA) mutation in mitochondrial encephalomyopathy (ME) with lactic acidosis and stroke-like episodes (MELAS) is m.3243A>G. In the future, the incidence of patients with cerebral infarction and diabetes mellitus is expected to increase tremendously. Additionally, the A3243G mutation typical of diabetes is estimated to be present in approximately 2% of all diabetes patients, which suggests that the potential disease population with a mitochondrial disorder is greater than previously thought, and there may have been many cases among the elderly that were misdiagnosed. Considering this background, MELAS with the onset of stroke-like episodes should be considered an important differential diagnosis for elderly patients with cerebral infarction, although it might have been overlooked until now. A 68-year-old Japanese female developed convulsive seizures and was admitted to Hospital of International University of Health and Welfare for epilepsy. She had been hospitalized twice in the previous year for cerebral infarction and seizures. She experienced sensorineural hearing loss at a young age. Thus, although she was elderly, we suspected MELAS and detected elevations of pyruvic and lactic acid. A genetic test revealed a point mutation in the mtDNA (m.3243A>G) that led to a definitive diagnosis of MELAS. To date, MELAS has been regarded as a disease of the relatively young. The incidence of patients with cerebral infarction and diabetes mellitus is expected to greatly increase. Thus, we should evaluate cerebral infarction in the elderly with caution to prevent missed diagnoses of MELAS.

A Mitochondrial Disorder in a Middle Age Iranian Patient: Report of a Rare Case

Introduction

Mitochondrial encephalopathy, lactic acidosis, and stroke-like episodes (MELAS) can involve multiple systems and cause stroke-like episodes and status epilepticus.

Case Presentation

A 48-year-old female with history of early fatigability, migraine-type headaches, and bilateral sensory-neural hearing loss presented 3 episodes of serial seizures. On admission she was affected by Wernicke aphasia and, then, right hemiparesis. Investigations showed elevated arterial lactate and ragged red fibers on muscle biopsy.

Conclusion

Though more commonly diagnosed during childhood, some cases of adult-onset MELAS syndrome are reported. This syndrome should be considered in patients with stroke-like events in adults without cerebrovascular risk factors and difficult-to-treat seizures.

Cortical venous disease severity in MELAS syndrome correlates with brain lesion development

PURPOSE

MELAS syndrome is a mitochondrial disorder typified by recurrent stroke-like episodes, seizures, and progressive brain injury. Abnormal mitochondria have been found in arterial walls implicating a vasculogenic etiology. We have observed abnormal cortical vein T2/FLAIR signal in MELAS patients, potentially representing wall thickening and sluggish flow. We sought to examine the relationship of hyperintense veins and brain lesions in MELAS.

METHODS

Imaging databases at two children's hospitals were searched for brain MRIs from MELAS patients. Artifact, sedated exams, and lack of 2D-T2/FLAIR sequences were exclusion criteria. Each exam was assigned a venous score based on number of T2/FLAIR hyperintense veins: 1 = <10, 2 = 10 to 20, 3 = >20. Cumulative brain lesions and venous score in MELAS and aged-matched normal exams were compared by Mann-Whitney test.

RESULTS

A total of 106 exams from 14 unique MELAS patients (mean 16 ± 3 years) and 30 exams from normal aged-matched patients (mean 15 ± 3 years) were evaluated. Median venous score between MELAS and control patients significantly differed (3 versus 1; p < 0.001). In the MELAS group, venous score correlated with presence (median = 3) or absence (median = 1) of cumulative brain lesions. In all 8 MELAS patients who developed lesions, venous hyperintensity was present prior to, during, and after lesion onset. Venous score did not correlate with brain lesion acuity.

CONCLUSION

Abnormal venous signal correlates with cumulative brain lesion severity in MELAS syndrome. Cortical venous stenosis, congestion, and venous ischemia may be mechanisms of brain injury. Identification of cortical venous pathology may aid in diagnosis and could be predictive of lesion development.

The clinical and genetic characteristics in children with mitochondrial disease in China

Mitochondrial disease was a clinically and genetically heterogeneous group of diseases, thus the diagnosis was very difficult to clinicians. Our objective was to analyze clinical and genetic characteristics of children with mitochondrial disease in China. We tested 141 candidate patients who have been suspected of mitochondrial disorders by using targeted next-generation sequencing (NGS), and summarized the clinical and genetic data of gene confirmed cases from Neurology Department, Beijing Children's Hospital, Capital Medical University from October 2012 to January 2015. In our study, 40 cases of gene confirmed mitochondrial disease including eight kinds of mitochondrial disease, among which Leigh syndrome was identified to be the most common type, followed by mitochondrial encephalomyopathy, lactic acidosis, and stroke-like episodes (MELAS). The age-of-onset varies among mitochondrial disease, but early onset was common. All of 40 cases were gene confirmed, among which 25 cases (62.5%) with mitochondrial DNA (mtDNA) mutation, and 15 cases (37.5%) with nuclear DNA (nDNA) mutation. M.3243A>G (n=7) accounts for a large proportion of mtDNA mutation. The nDNA mutations include SURF1 (n=7), PDHA1 (n=2), and NDUFV1, NDUFAF6, SUCLA2, SUCLG1, RRM2B, and C12orf65, respectively.

Preliminary Study of Neurodevelopmental Outcomes and Parenting Stress in Pediatric Mitochondrial Disease

BACKGROUND

Little is known regarding the neuropsychological profiles of pediatric patients with mitochondrial diseases or their parents, information that is crucial for improving the quality of life (QOL) for both patients and parents. We aimed to delineate neurodevelopment and psychological comorbidity in children with mitochondrial diseases in the preliminary investigation of adequate intervention methods, better prognoses, and improved QOL for both patients and parents.

METHODS

Seventy children diagnosed with mitochondrial diseases were neuropsychologically evaluated. Neurocognitive (development, intelligence) and psychological (behavior, daily living function, maternal depression, parenting stress) functions were analyzed. Clinical variables, including the first symptom, epileptic classification, organ involvement, lactic acidosis, brain magnetic resonance imaging findings, muscle pathology, biochemical enzyme assay results, and syndromic diagnosis of mitochondrial diseases, were also reviewed.

RESULTS

Prediagnostic assessments indicated that cognitive and psychomotor developments were significantly delayed. Group mean full scale intelligence quotient (IQ) scores indicated mild levels of intellectual disability, borderline levels of verbal IQ impairment, and mild levels of intellectual disability on performance IQ. Many children exhibited clinically significant levels of behavioral problems, whereas mothers of children with mitochondrial diseases exhibited significant increases in parenting stress relative to mothers of healthy children. Furthermore, 65% of mothers exhibited significant levels of depression. Early onset of the first symptoms, diffuse brain atrophy, and drug-resistant epilepsy negatively influenced neurodevelopmental and adaptive functions.

CONCLUSION

Better understanding of the functional levels and profiles of neurodevelopment and psychological comorbidity in children with mitochondrial diseases in the prediagnostic period is essential for adequate support and QOL of children with mitochondrial diseases and their parents.

Early Onset of Diabetes Mellitus Accelerates Cognitive Decline in Japanese Patients with Mitochondrial Myopathy, Encephalopathy, Lactic Acidosis, and Stroke-Like Episodes

Approximately 80% of patients with mitochondrial myopathy, encephalopathy, lactic acidosis, and stroke-like episodes (MELAS) carry the A3243G mutation in the mitochondrial tRNALeu (UUR) gene. Conversely, this mutation has also been identified as one of the most prevalent genetic abnormalities in patients with diabetes mellitus. Mitochondrial diabetes mellitus complicated with MELAS is relatively common, and 12.5% of patients with the A3243G mutation develop MELAS after being diagnosed with diabetes mellitus. However, the clinical impact of diabetes mellitus in MELAS patients remains unclear. Therefore, we retrospectively studied 14 Japanese MELAS patients with the A3243G mutation: three men and eleven women, with the mean age of 48.0 (± 15.4) years. Eight patients had been diagnosed with diabetes mellitus prior to the diagnosis of mitochondrial disease, and all of them were treated with insulin. The other six included four patients with concurrent diagnosis of diabetes and mitochondrial disease, one patient diagnosed with diabetes after the diagnosis of mitochondrial disease, and one patient without developing diabetes currently. We thus compared the patients' characteristics between those with and without early onset of diabetes mellitus. Cognitive decline (75.0% vs. 0%; p = 0.03) and poor glycemic control with severe hypoglycemic events (75.0% vs. 16.7%; p = 0.05) were more common in MELAS patients with a prior diagnosis of diabetes than in those without the prior diagnosis of diabetes. Our data suggest that the latent progress of cognitive decline is accelerated because of early onset of diabetes mellitus in MELAS patients.

Long-term Developmental Trends of Pediatric Mitochondrial Diseases: The Five Stages of Developmental Decline

Mitochondrial diseases (MDs) are a heterogeneous group of progressive multisystem disorders caused by impaired mitochondrial function. This study aimed to evaluate the clinical course and long-term development of 53 pediatric patients with MDs. Developmental function was evaluated at nine time points (two pre-diagnosis, one at diagnosis, and six post-diagnosis), with the developmental quotient (DQ) from the Korean infant and child development test (KICDT) assessing a child’s developmental age (rather than chronological age). Additionally, disease-related clinical variables were reviewed, and clinical progress was determined through observation. Subgroup analyses by epilepsy severity, syndromic diagnosis, diffuse brain atrophy, and clinical rating were performed. The pre- and post-diagnosis results were compared by the paired t-test and Bonferroni correction. The pre-diagnostic, diagnostic, and post-diagnostic evaluations were compared using repeated measures ANOVA. Patients with diffuse brain atrophy at the first pre-diagnostic and second post-diagnostic evaluations showed lower DQs. Compared with patients with a mildly or severely deteriorating clinical course, those with an improving or static clinical course presented higher DQs at the pre-diagnostic and diagnostic evaluations. The age at onset of the first symptom correlated positively with the DQ post-diagnosis. Follow-up revealed consistent patterns of significant developmental deterioration during the lead time to diagnosis, with no significant decline post-diagnosis. The DQ is a feasible predictor and a measure of long-term functional development in children with MD. Early initiation of treatment may minimize developmental regression.

Nationwide epidemiological survey of Leber hereditary optic neuropathy in Japan

BACKGROUND

Leber hereditary optic neuropathy (LHON) is a maternally inherited optic neuropathy that leads to central loss of vision, predominantly in young males. Most LHON cases have one of three primary point mutations in mitochondrial DNA (mtDNA). The annual incidence and prevalence of LHON in Japan are not known. Thus, we estimated the annual incidence of molecularly confirmed LHON in Japan during 2014.

METHODS

Sequential questionnaires were sent to 1397 facilities, which included all of the university hospitals in Japan, and they were certified by either the Japanese Ophthalmological Society or the Japanese Neuro-Ophthalmological Society. We calculated the incidence number (I_r) as the number of patients who developed LHON in 2014 and its 95% confidence interval.

RESULTS

We received 861 responses to the first questionnaire, where 49 facilities reported 72 cases (67 were male and 5 were female) of newly developed LHON during 2014. I_r was calculated as 117, and the 95% confidence interval ranged from 81 to 153. For the second questionnaire, responses were received from 30 facilities, where the median age at onset was 38 years for males and 30 years for females, and 86.5% of cases possessed the mtDNA ND4/G11778A mutation.

CONCLUSION

Approximately 120 cases of newly developed LHON were reported during 2014 in Japan, and 93.2% were males.

Recurrent Alternate-Sided Homonymous Hemianopia Due to Mitochondrial Encephalomyopathy with Lactic Acidosis and Stroke-Like Episodes (MELAS): A Case Report

Mitochondrial encephalomyopathy with lactic acidosis and stroke-like episodes (MELAS) can rarely cause alternate-sided homonymous hemianopia due to stroke-like episodes involving the occipital lobes, as reported in three previously published cases. The authors report an interesting case of a 16-year-old presenting with myoclonic epilepsy due to MELAS with the rare ND3 mitochondrial mutation T10191C, with recurrent alternate-sided homonymous hemianopia. Visual field and corresponding magnetic resonance imaging (MRI) findings are presented. To the authors' knowledge, this is the first report of recurrent alternate-sided homonymous hemianopia in MELAS with documented visual field and MRI findings with resolution between each episode.

Other cerebrovascular occlusive disease

In this chapter we review the optimal imaging modalities for subacute and chronic stroke. We discuss the utility of computed tomography (CT) and multimodal CT imaging. Further, we analyze the importance of specific magnetic resonance imaging sequences, such as diffusion-weighted imaging for acute ischemic stroke, T2/fluid-attenuated inversion recovery for subacute and chronic stroke, and susceptibility imaging for detection of intracranial hemorrhages. Different ischemic stroke mechanisms are reviewed, and how these imaging modalities may aid in the determination of such. Further, we analyze how topographic patterns in ischemic stroke may provide important clues to the diagnosis, in addition to the temporal evolution of the stroke. Lastly, specific cerebrovascular occlusive diseases are reviewed, with emphasis on the optimal imaging modalities and their findings in each condition.

Mitochondrial disease and endocrine dysfunction

Mitochondria are critical organelles for endocrine health; steroid hormone biosynthesis occurs in these organelles and they provide energy in the form of ATP for hormone production and trafficking. Mitochondrial diseases are multisystem disorders that feature defective oxidative phosphorylation, and are characterized by enormous clinical, biochemical and genetic heterogeneity. To date, mitochondrial diseases have been found to result from >250 monogenic defects encoded across two genomes: the nuclear genome and the ancient circular mitochondrial genome located within mitochondria themselves. Endocrine dysfunction is often observed in genetic mitochondrial diseases and reflects decreased intracellular production or extracellular secretion of hormones. Diabetes mellitus is the most frequently described endocrine disturbance in patients with inherited mitochondrial diseases, but other endocrine manifestations in these patients can include growth hormone deficiency, hypogonadism, adrenal dysfunction, hypoparathyroidism and thyroid disease. Although mitochondrial endocrine dysfunction frequently occurs in the context of multisystem disease, some mitochondrial disorders are characterized by isolated endocrine involvement. Furthermore, additional monogenic mitochondrial endocrine diseases are anticipated to be revealed by the application of genome-wide next-generation sequencing approaches in the future. Understanding the mitochondrial basis of endocrine disturbance is key to developing innovative therapies for patients with mitochondrial diseases.

Cause of Death in Children With Mitochondrial Diseases

BACKGROUND

We investigated the clinical characteristics that represent risk factors for death in pediatric patients with mitochondrial diseases.

METHODS

The medical records of mitochondrial disease pediatric patients attended between 2006 and 2015 (n = 221) were reviewed for clinical characteristics, diagnosis, hospitalization, follow-up, survival, and cause of death.

RESULTS

The global mortality rate in the cohort was 14% (average age at death, six years). By syndromic diagnosis, the mortality rates were as follows: Leigh syndrome, 17% (15 of 88); mitochondrial encephalomyopathy, lactic acidosis, and stroke-like episodes, 50% (two of four); and nonspecific mitochondrial disease, 11% (14 of 129). Data regarding 31 patients (17 males) were included in the analysis of cause of death. The age at symptom onset, lead time to diagnosis, duration of illness, and duration of life were 1.8 ± 2.0, 1.7 ± 1.5, 4.3 ± 2.7, and 6.1 ± 2.9 years, respectively. The most common causes of death were sepsis, pneumonia, disseminated intravascular coagulation, and sudden unexpected death (55%, 42%, 29%, and 29%, respectively). Early death (age six years or younger) was associated with lesions in the thalamus, number of organs involved, and Leigh syndrome.

CONCLUSIONS

Careful monitoring of the medical condition and early intervention are key to improving survival in pediatric patients with mitochondrial disease.

Arginine and citrulline for the treatment of MELAS syndrome

MELAS (mitochondrial encephalomyopathy, lactic acidosis, and stroke-like episodes) syndrome is a maternally inherited mitochondrial disease with a broad spectrum of manifestations. In addition to impaired energy production, nitric oxide (NO) deficiency occurs in MELAS syndrome and leads to impaired blood perfusion in microvasculature that can contribute to several complications including stroke-like episodes, myopathy, and lactic acidosis. The supplementation of NO precursors, L-arginine and L-citrulline, increases NO production and hence can potentially have therapeutic utility in MELAS syndrome. L-citrulline raises NO production to a greater extent than L-arginine; therefore, L-citrulline may have a better therapeutic effect. The clinical effect of L-citrulline has not yet been studied and clinical studies on L-arginine, which are limited, only evaluated the stroke-like episodes aspect of the disease. Controlled studies are still needed to assess the clinical effects of L-arginine and L-citrulline on different aspects of MELAS syndrome.

The many faces of paediatric mitochondrial disease on neuroimaging

The knowledge about the genetic spectrum underlying paediatric mitochondrial diseases is rapidly growing. As a consequence, the range of neuroimaging findings associated with mitochondrial diseases became extremely broad. This has important implications for radiologists and clinicians involved in the care of these patients. Here, we provide a condensed overview of brain magnetic resonance imaging (MRI) findings in children with genetically confirmed mitochondrial diseases. The neuroimaging spectrum ranges from classical Leigh syndrome with symmetrical lesions in basal ganglia and/or brain stem to structural abnormalities including cerebellar hypoplasia and corpus callosum dysgenesis. We highlight that, although some imaging patterns can be suggestive of a genetically defined mitochondrial syndrome, brain MRI-based candidate gene prioritization is only successful in a subset of patients.

Epilepsy Characteristics and Clinical Outcome in Patients With Mitochondrial Encephalomyopathy, Lactic Acidosis, and Stroke-Like Episodes (MELAS)

BACKGROUND

Epileptic seizures in patients with mitochondrial encephalomyopathy, lactic acidosis, and stroke-like episodes (MELAS) are heterogeneous with no pathognomonic features. We reviewed epilepsy characteristics and clinical outcome exclusively in a pediatric population.

METHODS

Twenty-two children and adolescents (13 males) with confirmed mitochondrial encephalomyopathy, lactic acidosis, and stroke-like episodes due to mitochondrial DNA A3243G mutation and epilepsy were recruited. Clinical data including seizure semiology, treatment response, neuroimaging findings, and electroencephalography were analyzed. We also examined the effect of the age at seizure onset and initial symptoms on the clinical variables.

RESULTS

Seizure semiology and electroencephalography abnormalities showed no syndrome-specific findings. Focal seizures occurred in 21 of 22 subjects (95.5%), whereas generalized seizures developed in seven of 22 subjects (31.8%). Twenty of 22 subjects (90.9%) achieved partial to complete reduction of clinical seizures for more than one year with a combination of more than two antiepileptic drugs. The subgroup with earlier seizure onset presented significantly earlier and showed significantly higher rates of drug-resistant epilepsy compared with the late onset group, although there were no significant differences in the initial symptoms. The subjects with severe epileptic conditions tended to have more severe clinical dysfunction and more severe organ involvement.

CONCLUSIONS

Both focal and generalized seizures occurred in patients with MELAS. Epilepsy in this population is drug resistant, but a certain degree of clinical seizure reduction was achievable with antiepileptic drugs, with more favorable outcomes than historically expected. Close observation and active epilepsy treatment of individuals with MELAS episodes and earlier seizure onset might improve the prognosis.

Mitochondrial diseases

Mitochondrial diseases are a group of genetic disorders that are characterized by defects in oxidative phosphorylation and caused by mutations in genes in the nuclear DNA (nDNA) and mitochondrial DNA (mtDNA) that encode structural mitochondrial proteins or proteins involved in mitochondrial function. Mitochondrial diseases are the most common group of inherited metabolic disorders and are among the most common forms of inherited neurological disorders. One of the challenges of mitochondrial diseases is the marked clinical variation seen in patients, which can delay diagnosis. However, advances in next-generation sequencing techniques have substantially improved diagnosis, particularly in children. Establishing a genetic diagnosis allows patients with mitochondrial diseases to have reproductive options, but this is more challenging for women with pathogenetic mtDNA mutations that are strictly maternally inherited. Recent advances in in vitro fertilization techniques, including mitochondrial donation, will offer a better reproductive choice for these women in the future. The treatment of patients with mitochondrial diseases remains a challenge, but guidelines are available to manage the complications of disease. Moreover, an increasing number of therapeutic options are being considered, and with the development of large cohorts of patients and biomarkers, several clinical trials are in progress.

Migratory stroke-like lesions in a case of adult-onset mitochondrial encephalomyopathy, lactic acidosis, and stroke-like episodes (MELAS) syndrome and a review of imaging findings

Imaging findings of adult-onset mitochondrial encephalomyopathy, lactic acidosis, and stroke-like episodes (MELAS) syndrome is poorly documented. The authors present a 48-year-old woman with subacute onset of word-finding difficulties and right arm stiffness. Magnetic resonance imaging performed 2 weeks prior revealed left temporal lobe diffusion and fluid-attenuated inversion recovery hyperintensity predominantly involving the cortex. The apparent diffusion coefficient map showed preserved signal in the temporal cortex. Subsequent magnetic resonance imagings demonstrated a new diffusion signal abnormality extending to the left parietal cortex and occipital cortex with resolving diffusion hyperintensity in the temporal lobe. MR spectroscopy showed scattered areas of lactate deposition. Diagnosis of MELAS syndrome was confirmed by genetic analysis. Fluctuating, migratory stroke-like lesions with a predilection for the parietal, temporal, and occipital cortex that do not conform to a vascular territory and a lactate spike at 1.3 ppm on MR spectroscopy are characteristic of MELAS syndrome. Preserved signal intensity on apparent diffusion coefficient is useful to distinguish MELAS syndrome from ischemic infarction where the signal is typically reduced.

Distinctive distribution of brain volume reductions in MELAS and mitochondrial DNA A3243G mutation carriers: A voxel-based morphometric study

OBJECTIVE

The aim of this study was to investigate the clinically latent brain atrophy of patients with mitochondrial encephalopathy, lactic acidosis, and stroke-like episodes (MELAS) harboring a mitochondrial DNA A3243G mutation (A3243G) and A3243G carriers without stroke-like episodes (SEs).

METHODS

We used voxel-based morphometry (VBM) with magnetic resonance imaging to investigate gray matter (GM) and white matter (WM) volume reductions in four MELAS patients and in five A3243G carriers compared to 16 healthy controls. In addition, we investigated the regions of previous SEs using conventional MRI.

RESULTS

All four MELAS patients showed significant GM volume reductions in the left superior parietal lobule (SPL), right precuneus, right middle temporal gyrus (MTG), and bilateral posterior lobes of the cerebellum. These areas of GM volume reduction were beyond the regions of previous SEs. As for A3243G carriers, GM volume reductions in the left SPL, right precuneus, right MTG, and bilateral posterior lobes of the cerebellum were detected in three, one, two, and five subjects, respectively. All four MELAS patients showed significant WM volume reductions in the bilateral or unilateral temporal sub-gyral regions, which were included in the regions of previous SEs. No A3243G carriers showed WM volume reductions.

CONCLUSION

The distribution patterns of GM volume reductions in VBM may reflect a common vulnerability of the brains among MELAS patients and A3243G carriers.

The phenotypic spectrum of fifty Czech m.3243A>G carriers

BACKGROUND

Mitochondrial myopathy, Encephalopathy, Lactic Acidosis and Stroke-like episodes syndrome (MELAS) is a common mitochondrial disorder with varying multisystemic clinical manifestation. We present a comprehensive clinical picture of 50 Czech m.3243A>G carriers with emphasis on the sequence of symptoms in symptomatic patients.

RESULTS

Symptoms developed in 33 patients (66%) and 17 carriers remained unaffected (34%). The age of onset varied from 1month to 47years of age, with juvenile presentation occurring in 53% of patients. Myopathy was the most common presenting symptom (18%), followed by CPEO/ptosis and hearing loss, with the latter also being the most common second symptom. Stroke-like episodes (SLE) occurred in fourteen patients, although never as a first symptom, and were frequently preceded by migraines (58%). Rhabdomyolysis developed in two patients. The second symptom appeared 5.0±8.3years (range 0-28years) after the first, and the interval between the second and third symptom was 2.0±6.0years (range 0-21years). Four of our patients remained monosymptomatic up to 12years of follow-up. The sequence of symptoms according to their time of manifestation was migraines, myopathy, seizures, CPEO/ptosis, SLE, hearing loss, and diabetes mellitus. The average age at death was 32.4±17.7years (range 9-60years) in the juvenile form and 44.0±12.7years (range 35-53years) in the adult form. Some patients with SLE harboured very low heteroplasmy levels in various tissues. No threshold for any organ dysfunction could be determined based on these levels.

CONCLUSIONS

Sufficient knowledge of the timeline of the natural course of MELAS syndrome may improve the prediction and management of symptoms in patients with this mitochondrial disease.

A comparison of current serum biomarkers as diagnostic indicators of mitochondrial diseases

OBJECTIVE

To directly compare the diagnostic utility of growth differentiation factor-15 (GDF-15) with our previous fibroblast growth factor-21 (FGF-21) findings in the same adult mitochondrial disease cohort.

METHODS

Serum GDF-15 levels were measured using a quantitative ELISA. Statistical analyses of GDF-15 data were compared with our published FGF-21 findings.

RESULTS

Median serum GDF-15 concentrations were elevated in patients with mitochondrial disease and differed between all experimental groups, mirroring group results for FGF-21. There was a difference between patients diagnosed by muscle biopsy and genetic diagnosis, suggesting that serum GDF-15 measurement may be more broadly specific for mitochondrial disease than for muscle manifesting mitochondrial disease, in contrast to FGF-21. GDF-15 showed a markedly higher diagnostic odds ratio when compared with FGF-21 (75.3 vs 45.7), was a better predictor of disease based on diagnostic sensitivity (77.8% vs 68.5%), and outperformed FGF-21 on receiver operating characteristic curve analysis (area under the curve 94.1% vs 91.1%). Combining both biomarkers did not improve the area under the curve remarkably over GDF-15 alone. GDF-15 was the best predictor of mitochondrial disease (p < 0.002) following multivariate logistic regression analysis.

CONCLUSIONS

GDF-15 outperforms FGF-21 as an indicator of mitochondrial diseases. Our data suggest that GDF-15 is generally indicative of inherited mitochondrial disease regardless of clinical phenotype, whereas FGF-21 seems to be more indicative of mitochondrial disease when muscle manifestations are present.

CLASSIFICATION OF EVIDENCE

This study provides Class III evidence that serum GDF-15 accurately distinguishes patients with mitochondrial diseases from those without them.

Impaired nitric oxide production in children with MELAS syndrome and the effect of arginine and citrulline supplementation

Mitochondrial encephalomyopathy, lactic acidosis, and stroke-like episodes (MELAS) syndrome is one of the most frequent maternally inherited mitochondrial disorders. The pathogenesis of this syndrome is not fully understood and believed to result from several interacting mechanisms including impaired mitochondrial energy production, microvasculature angiopathy, and nitric oxide (NO) deficiency. NO deficiency in MELAS syndrome is likely to be multifactorial in origin with the decreased availability of the NO precursors, arginine and citrulline, playing a major role. In this study we used stable isotope infusion techniques to assess NO production in children with MELAS syndrome and healthy pediatric controls. We also assessed the effect of oral arginine and citrulline supplementations on NO production in children with MELAS syndrome. When compared to control subjects, children with MELAS syndrome were found to have lower NO production, arginine flux, plasma arginine, and citrulline flux. In children with MELAS syndrome, arginine supplementation resulted in increased NO production, arginine flux, and arginine concentration. Citrulline supplementation resulted in a greater increase of these parameters. Additionally, citrulline supplementation was associated with a robust increase in citrulline concentration and flux and de novo arginine synthesis rate. The greater effect of citrulline in increasing NO production is due to its greater ability to increase arginine availability particularly in the intracellular compartment in which NO synthesis takes place. This study, which is the first one to assess NO metabolism in children with mitochondrial diseases, adds more evidence to the notion that NO deficiency occurs in MELAS syndrome, suggests a better effect for citrulline because of its greater role as NO precursor, and indicates that impaired NO production occurs in children as well as adults with MELAS syndrome. Thus, the initiation of treatment with NO precursors may be beneficial earlier in life. Controlled clinical trials to assess the therapeutic effects of arginine and citrulline on clinical complications of MELAS syndrome are needed.

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.

Growth differentiation factor 15 as a useful biomarker for mitochondrial disorders

Objective

The diagnosis of mitochondrial disorders (MDs) is occasionally difficult because patients often present with solitary, or a combination of, symptoms caused by each organ insufficiency, which may be the result of respiratory chain enzyme deficiency. Growth differentiation factor 15 (GDF‐15) has been reported to be elevated in serum of patients with MDs. In this study, we investigated whether GDF‐15 is a more useful biomarker for MDs than several conventional biomarkers.

Methods

We measured the serum levels of GDF‐15 and fibroblast growth factor 21 (FGF‐21), as well as other biomarkers, in 48 MD patients and in 146 healthy controls in Japan. GDF‐15 and FGF‐21 concentrations were measured by enzyme‐linked immunosorbant assay and compared with lactate, pyruvate, creatine kinase, and the lactate‐to‐pyruvate ratio. We calculated sensitivity and specificity and also evaluated the correlation based on two rating scales, including the Newcastle Mitochondrial Disease Rating Scale (NMDAS).

Results

Mean GDF‐15 concentration was 6‐fold higher in MD patients compared to healthy controls (2,711 ± 2,459 pg/ml vs 462.5 ± 141.0 pg/mL; p < 0.001). Using a receiver operating characteristic curve, the area under the curve was significantly higher for GDF‐15 than FGF‐21 and other conventional biomarkers. Our date suggest that GDF‐15 is the most useful biomarker for MDs of the biomarkers examined, and it is associated with MD severity.

Interpretation

Our results suggest that measurement of GDF‐15 is the most useful first‐line test to indicate the patients who have the mitochondrial respiratory chain deficiency. Ann Neurol 2015;78:Ann Neurol 2015;78:679–696

MELAS syndrome: Clinical manifestations, pathogenesis, and treatment options

Mitochondrial encephalomyopathy, lactic acidosis, and stroke-like episodes (MELAS) syndrome is one of the most frequent maternally inherited mitochondrial disorders. MELAS syndrome is a multi-organ disease with broad manifestations including stroke-like episodes, dementia, epilepsy, lactic acidemia, myopathy, recurrent headaches, hearing impairment, diabetes, and short stature. The most common mutation associated with MELAS syndrome is the m.3243A>G mutation in the MT-TL1 gene encoding the mitochondrial tRNA(Leu(UUR)). The m.3243A>G mutation results in impaired mitochondrial translation and protein synthesis including the mitochondrial electron transport chain complex subunits leading to impaired mitochondrial energy production. The inability of dysfunctional mitochondria to generate sufficient energy to meet the needs of various organs results in the multi-organ dysfunction observed in MELAS syndrome. Energy deficiency can also stimulate mitochondrial proliferation in the smooth muscle and endothelial cells of small blood vessels leading to angiopathy and impaired blood perfusion in the microvasculature of several organs. These events will contribute to the complications observed in MELAS syndrome particularly the stroke-like episodes. In addition, nitric oxide deficiency occurs in MELAS syndrome and can contribute to its complications. There is no specific consensus approach for treating MELAS syndrome. Management is largely symptomatic and should involve a multidisciplinary team. Unblinded studies showed that l-arginine therapy improves stroke-like episode symptoms and decreases the frequency and severity of these episodes. Additionally, carnitine and coenzyme Q10 are commonly used in MELAS syndrome without proven efficacy.

Development of pharmacological strategies for mitochondrial disorders

Mitochondrial diseases are an unusually genetically and phenotypically heterogeneous group of disorders, which are extremely challenging to treat. Currently, apart from supportive therapy, there are no effective treatments for the vast majority of mitochondrial diseases. Huge scientific effort, however, is being put into understanding the mechanisms underlying mitochondrial disease pathology and developing potential treatments. To date, a variety of treatments have been evaluated by randomized clinical trials, but unfortunately, none of these has delivered breakthrough results. Increased understanding of mitochondrial pathways and the development of many animal models, some of which are accurate phenocopies of human diseases, are facilitating the discovery and evaluation of novel prospective treatments. Targeting reactive oxygen species has been a treatment of interest for many years; however, only in recent years has it been possible to direct antioxidant delivery specifically into the mitochondria. Increasing mitochondrial biogenesis, whether by pharmacological approaches, dietary manipulation or exercise therapy, is also currently an active area of research. Modulating mitochondrial dynamics and mitophagy and the mitochondrial membrane lipid milieu have also emerged as possible treatment strategies. Recent technological advances in gene therapy, including allotopic and transkingdom gene expression and mitochondrially targeted transcription activator-like nucleases, have led to promising results in cell and animal models of mitochondrial diseases, but most of these techniques are still far from clinical application.

Inherited leukoencephalopathies with clinical onset in middle and old age

The currently widespread use of neuroimaging has led neurologists to often face the problem of the differential diagnosis of white matter diseases. There are various forms of leukoencephalopathies (vascular, inflammatory and immunomediated, infectious, metabolic, neoplastic) and sometimes white matter lesions are expression of a genetic disease. While many inherited leukoencephalopathies fall in the child neurologist's interest, others may have a delayed or even a typical onset in the middle or old age. This field is rapidly growing and, in the last few years, many new inherited white matter diseases have been described and genetically defined. A non-delayed recognition of middle and old age inherited leukoencephalopathies appears important to avoid unnecessary tests and therapies in the patient and to possibly anticipate the diagnosis in relatives. The aim of this review is to provide a guide to direct the diagnostic process when facing a patient with a suspicion of an inherited form of leukoencephalopathy and with clinical onset in middle or old age. Based on a MEDLINE search from 1990 to 2013, we identified 24 middle and old age onset inherited leukoencephalopathies and reviewed in this relation the most recent findings focusing on their differential diagnosis. We provide summary tables to use as a check list of clinical and neuroimaging findings that are most commonly associated with these forms of leukoencephalopathies. When present, we reported specific characteristics of single diseases. Several genetic diseases may be suspected in patients with middle or old age and white matter abnormalities. In only few instances, pathognomonic clinical or associated neuroimaging features help identifying a specific disease. Therefore, a comprehensive knowledge of the characteristics of these inherited white matter diseases appears important to improve the diagnostic work-up, optimize the choice of genetic tests, increase the number of diagnosed patients, and stimulate the research interest in this field.

Efficacy of pyruvate therapy in patients with mitochondrial disease: a semi-quantitative clinical evaluation study

BACKGROUND

Disorders of oxidative phosphorylation (OXPHOS) cause an increase in the NADH/NAD(+) ratio, which impairs the glycolysis pathway. Treatment with pyruvate is expected to decrease the ratio and thereby restore glycolysis. There are some case reports on the efficacy of pyruvate treatment for mitochondrial diseases. However, few of these reports assessed their results using a standardized scale.

METHODS

We monitored 4 bedridden patients with OXPHOS disorders who continued therapies of 0.5-1.0 g/kg/day of sodium pyruvate for more than 12 months. The efficacies of these treatments were evaluated with the Newcastle Pediatric Mitochondrial Disease Scale and the Gross Motor Function Measure with 88 items.

RESULTS

The ages of the patients at the treatment initiation ranged from 8-100 months. Of the 4 patients, 3 exhibited improvements within 1-3 months from the initiation of treatment. Among these 3 patients, one maintained the improvement for over 2 years. The remaining 2 regressed 3-6 months after the initiation of treatment. The blood lactate/pyruvate ratios did not correlate with the efficacy of treatment.

CONCLUSION

Pyruvate was effective even in bedridden patients with OXPHOS disorders, at least in the short term. Clinical trials with more patients and less severe disabilities are necessary to evaluate the long-term efficacy of this treatment. Biomarkers other than lactate and pyruvate need to be identified to biochemically monitor the efficacy of this treatment.

[Effectiveness of midazolam for L-arginine-resistant headaches during stroke-like episodes in MELAS: a case report]

A 14-year-old girl was referred to us with severe migraine-like headaches associated with vomiting and right homonymous hemianopsia. On admission, MRI examination showed high signals in the left occipital cortex and subcortex on T2-weighted images, without reduction of apparent diffusion coefficient suggestive of cerebral infarction. Her EEG demonstrated periodic sharp waves in the left posterior region, and laboratory tests revealed she had increased levels of lactic and pyruvic acid both in blood plasma and CSF. Gene analysis confirmed mitochondrial DNA A3243G mutation. Based on this data, we diagnosed her as having mitochondrial myopathy, encephalopathy, lactic acidosis and a stroke-like episode (MELAS). L-arginine infusion was unsuccessful for her severe headaches, which remained prolonged. She received a low dose (0.05 mg/kg/h) midazolam infusion, resulting in immediate improvement and the disappearance of headaches and abnormal EEG findings. By the age of 18, she had been readmitted eight times for stroke-like episodes accompanied by headaches. While L-arginine infusions alleviated her headaches when administered on day 1 of her episodes, they were not effective when started on or after day 2. Her L-arginine-resistant headaches were relieved by midazolam. Although the pathogenesis of headaches in MELAS is still unknown, neuronal hyperexcitability and trigeminovascular activation are considered important. Midazolam may play a role in suppressing neuronal hyperexcitability and trigeminovascular activation. Treatment with midazolam is advisable for headaches in patients with MELAS, in the event that L-arginine therapy is unsuccessful.

Disease progression in patients with single, large-scale mitochondrial DNA deletions

Single, large-scale deletions of mitochondrial DNA are a common cause of mitochondrial disease and cause a broad phenotypic spectrum ranging from mild myopathy to devastating multi-system syndromes such as Kearns-Sayre syndrome. Studies to date have been inconsistent on the value of putative predictors of clinical phenotype and disease progression such as mutation load and the size or location of the deletion. Using a cohort of 87 patients with single, large-scale mitochondrial DNA deletions we demonstrate that a variety of outcome measures such as COX-deficient fibre density, age-at-onset of symptoms and progression of disease burden, as measured by the Newcastle Mitochondrial Disease Adult Scale, are significantly (P < 0.05) correlated with the size of the deletion, the deletion heteroplasmy level in skeletal muscle, and the location of the deletion within the genome. We validate these findings with re-analysis of 256 cases from published data and clarify the previously conflicting information of the value of these predictors, identifying that multiple regression analysis is necessary to understand the effect of these interrelated predictors. Furthermore, we have used mixed modelling techniques to model the progression of disease according to these predictors, allowing a better understanding of the progression over time of this strikingly variable disease. In this way we have developed a new paradigm in clinical mitochondrial disease assessment and management that sidesteps the perennial difficulty of ascribing a discrete clinical phenotype to a broad multi-dimensional and progressive spectrum of disease, establishing a framework to allow better understanding of disease progression.

Increased Prevalence of Hypertension in Young Adults with High Heteroplasmy Levels of the MELAS m.3243A>G Mutation

BACKGROUND

The pathophysiology of hypertension in patients with mitochondrial diseases is different from that of the general population. Growing evidence exists linking mtDNA, its mutations, and mitochondrial dysfunction to the pathogenesis of hypertension. No reports on the prevalence of hypertension in late-onset mtDNA diseases have been described.

METHODS

We performed a retrospective chart review of adult patients with late-onset mtDNA diseases between January 1999 and January 2012 at our center. We grouped them into age categories to allow comparison with previously reported Canadian Health Measures Survey (CHMS) prevalence data.

RESULTS

Twenty-three subjects with hypertension were identified for a crude prevalence of 39.7 % (95 % CI 27-53 %) as compared to the CHMS age-predicted prevalence of 30.5 %. When analyzed by individual age group, there were no significant differences between the observed and the CHMS predicted prevalence rates in the 40 years and older cohorts (age category 40-59, p = 0.63; age category 60-79, p = 0.85). However, hypertension rates were significantly higher than predicted in the under 40 years cohort (55.6 vs. 2.8 %, p < 0.001, CI 21-86 %), in which hypertensive patients with the MELAS m.3243A>G mutation were significantly clustered (p < 0.01). This younger MELAS cohort (n = 4, mean age = 24 years) with hypertension had heteroplasmy levels (mean = 68 %) that were significantly higher than the levels found in the older non-hypertensive MELAS cohort (n = 8, mean age = 52 years, mean = 33 %) (p = 0.04).

CONCLUSION

Relative to age, gender, and mtDNA disease subtype, young adults with high heteroplasmy levels of the MELAS m.3243A>G mutation demonstrate an increased prevalence of hypertension. Further prospective data are needed to confirm this initial finding, which has potentially important treatment implications.

Endocrine manifestations related to inherited metabolic diseases in adults

Most inborn errors of metabolism (IEM) are recessive, genetically transmitted diseases and are classified into 3 main groups according to their mechanisms: cellular intoxication, energy deficiency, and defects of complex molecules. They can be associated with endocrine manifestations, which may be complications from a previously diagnosed IEM of childhood onset. More rarely, endocrinopathies can signal an IEM in adulthood, which should be suspected when an endocrine disorder is associated with multisystemic involvement (neurological, muscular, hepatic features, etc.). IEM can affect all glands, but diabetes mellitus, thyroid dysfunction and hypogonadism are the most frequent disorders. A single IEM can present with multiple endocrine dysfunctions, especially those involving energy deficiency (respiratory chain defects), and metal (hemochromatosis) and storage disorders (cystinosis). Non-autoimmune diabetes mellitus, thyroid dysfunction and/or goiter and sometimes hypoparathyroidism should steer the diagnosis towards a respiratory chain defect. Hypogonadotropic hypogonadism is frequent in haemochromatosis (often associated with diabetes), whereas primary hypogonadism is reported in Alström disease and cystinosis (both associated with diabetes, the latter also with thyroid dysfunction) and galactosemia. Hypogonadism is also frequent in X-linked adrenoleukodystrophy (with adrenal failure), congenital disorders of glycosylation, and Fabry and glycogen storage diseases (along with thyroid dysfunction in the first 3 and diabetes in the last). This is a new and growing field and is not yet very well recognized in adulthood despite its consequences on growth, bone metabolism and fertility. For this reason, physicians managing adult patients should be aware of these diagnoses.