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Mitochondrial encephalopathy, lactic acidosis, and stroke-like episodes (MELAS) syndrome is a complex mitochondrial disorder characterized by a wide range of systemic manifestations. Key clinical features include recurrent stroke-like episodes, seizures, lactic acidosis, muscle weakness, exercise intolerance, sensorineural hearing loss, diabetes, and progressive neurological decline. MELAS is most commonly associated with mutations in mitochondrial DNA, particularly the m.3243A>G mutation in the MT-TL1 gene, which encodes tRNALeu (CUR). These mutations impair mitochondrial protein synthesis, leading to defective oxidative phosphorylation and energy failure at the cellular level. The clinical presentation and severity vary widely among patients, but the syndrome often results in significant morbidity and reduced life expectancy because of progressive neurological deterioration. Current management is largely focused on conservative care, including anti-seizure medications, arginine or citrulline supplementation, high-dose taurine, and dietary therapies. However, these therapies do not address the underlying genetic mutations, leaving many patients with substantial disease burden. Emerging experimental treatments, such as gene therapy and mitochondrial replacement techniques, aim to correct the underlying genetic defects and offer potential curative strategies. Further research is essential to understand the pathophysiology of MELAS, optimize current therapies, and develop novel treatments that may significantly improve patient outcomes and extend survival.

Mitochondrial encephalomyopathy, lactic acidosis, and stroke-like episode (MELAS) syndrome, caused by a single base substitution in mitochondrial DNA (m.3243A>G), is one of the most common maternally inherited mitochondrial diseases accompanied by neuronal damage due to defects in the oxidative phosphorylation system. There is no established treatment. Our previous study reported a superior restoration of mitochondrial function and bioenergetics in mitochondria-deficient cells using highly purified mesenchymal stem cells (RECs). However, whether such exogenous mitochondrial donation occurs in mitochondrial disease models and whether it plays a role in the recovery of pathological neuronal functions is unknown. Here, utilizing induced pluripotent stem cells (iPSC), we differentiated neurons with impaired mitochondrial function from patients with MELAS. MELAS neurons and RECs/mesenchymal stem cells (MSCs) were cultured under contact or non-contact conditions. Both RECs and MSCs can donate mitochondria to MELAS neurons, but RECs are more excellent than MSCs for mitochondrial transfer in both systems. In addition, REC-mediated mitochondrial transfer significantly restored mitochondrial function, including mitochondrial membrane potential, ATP/ROS production, intracellular calcium storage, and oxygen consumption rate. Moreover, mitochondrial function was maintained for at least three weeks. Thus, REC-donated exogenous mitochondria might offer a potential therapeutic strategy for treating neurological dysfunction in MELAS.

Mitochondrial disorders can present with a wide range of clinical and biochemical phenotypes. Mitochondrial DNA variants may be influenced by factors such as degree of heteroplasmy and tissue distribution. We present a four-generation family in which 10 individuals carry a pathogenic mitochondrial variant (m.5537_5538insT, MT-TW gene) with differing levels of heteroplasmy and clinical features. This genetic variant has been documented in two prior reports, both in individuals with Leigh syndrome. In the current family, three individuals have severe mitochondrial symptoms including Leigh syndrome (patient 1, 100% in blood), MELAS (patient 2, 97% heteroplasmy in muscle), and MELAS-like syndrome (patient 3, 50% heteroplasmy in blood and 100% in urine). Two individuals have mild mitochondrial symptoms (patient 4, 50% in blood and 67% in urine and patient 5, 50% heteroplasmy in blood and 30% in urine). We observe that this variant is associated with multiple mitochondrial presentations and phenotypes, including MELAS syndrome for which this variant has not previously been reported. We also demonstrate that the level of heteroplasmy of the mitochondrial DNA variant correlates with the severity of clinical presentation; however, not with the specific mitochondrial syndrome., (© 2023 The Authors. American Journal of Medical Genetics Part A published by Wiley Periodicals LLC.)

Mutations in mitochondrial (mt-)tRNAs frequently cause mitochondrial dysfunction. Mitochondrial myopathy, encephalopathy, lactic acidosis, and stroke-like episodes (MELAS), and myoclonus epilepsy associated with ragged red fibers (MERRF) are major clinical subgroups of mitochondrial diseases caused by pathogenic point mutations in tRNA genes encoded in mtDNA. We previously reported a severe reduction in the frequency of 5-taurinomethyluridine (τm5U) and its 2-thiouridine derivative (τm5s2U) in the anticodons of mutant mt-tRNAs isolated from the cells of patients with MELAS and MERRF, respectively. The hypomodified tRNAs fail to decode cognate codons efficiently, resulting in defective translation of respiratory chain proteins in mitochondria. To restore the mitochondrial activity of MELAS patient cells, we overexpressed MTO1, a τm5U-modifying enzyme, in patient-derived myoblasts. We used a newly developed primer extension method and showed that MTO1 overexpression almost completely restored the τm5U modification of the MELAS mutant mt-tRNALeu(UUR). An increase in mitochondrial protein synthesis and oxygen consumption rate suggested that the mitochondrial function of MELAS patient cells can be activated by restoring the τm5U of the mutant tRNA. In addition, we confirmed that MTO1 expression restored the τm5s2U of the mutant mt-tRNALys in MERRF patient cells. These findings pave the way for epitranscriptomic therapies for mitochondrial diseases., (© The Author(s) 2023. Published by Oxford University Press on behalf of Nucleic Acids Research.)

MELAS syndrome (Mitochondrial Encephalopathy, Lactic Acidosis and Stroke-like episodes) is one of the most frequent mitochondrial pathologies. Its diagnosis is based on the classic triad of symptoms its acronym stands for and the presence of ragged red fibres. There is currently no curative therapy for MELAS, and treatment focuses on managing complications that affect specific organs and functions. However, some immunonutrients can be used as a therapeutic alternative in patients with MELAS. We present a scientific literature review accompanied by the clinical case of a patient with dementia and seizures admitted to the intensive care unit., (Copyright © 2021 SEEN and SED. Published by Elsevier España, S.L.U. All rights reserved.)

Mitochondrial encephalomyopathy with lactic acidosis and stroke-like episodes (MELAS) is a disease that should be considered as a differential diagnosis to acute ischemic stroke taking into account its onset pattern and neurological symptoms, which are similar to those of an ischemic stroke. Technological advancements in neuroimaging modalities have greatly facilitated differential diagnosis between stroke and MELAS on diagnostic imaging. Stroke-like episodes in MELAS have the following features: (1) symptoms are neurolocalized according to lesion site; (2) epileptic seizures are often present; (3) lesion distribution is inconsistent with vascular territory; (4) lesions are common in the posterior brain regions; (5) lesions continuously develop in adjacent sites over several weeks or months; (6) neurological symptoms and stroke-like lesions tend to be reversible, as presented on magnetic resonance imaging; (7) the rate of recurrence is high; and; (8) brain dysfunction and atrophy are slowly progressive. The m.3243ANG mutation in the MT-TL1 gene encoding the mitochondrial tRNA Leu (UUR) is most commonly associated with MELAS. Although the precise pathophysiology is still unclear, one possible hypothesis for these episodes is a neuronal hyperexcitability theory, including neuron-astrocyte uncoupling. Supplementation, such as with L-arginine or taurine, has been proposed as preventive treatments for stroke-like episodes. As this disease is still untreatable and devastating, numerous drugs are being tested, and new gene therapies hold great promise for the future. This article contributes to the understanding of MELAS and its implications for clinical practice, by deepening their insight into the latest pathophysiological hypotheses and therapeutic developments., (© 2021. The Author(s), under exclusive licence to Springer Science+Business Media, LLC, part of Springer Nature.)

There have been considerations since the beginning of the Coronavirus pandemic that COVID-19 infection, like any other viral illness, can trigger neurological and metabolic decompensation in patients with mitochondrial diseases. At the time of writing, there were no published reports reviewing experiences and guidelines about management of COVID-19 infection in this patient population. We present a challenging case of an adult patient with a known diagnosis of Mitochondrial Encephalomyopathy, Lactic Acidosis and Stroke-like Episodes (MELAS) complicated by COVID-19 infection. She initially presented with altered mental status and vomiting and went on to develop a stroke-like episode, pancreatitis, and pneumatosis intestinalis. We review salient features of her hospitalization, including initiation of thromboprophylaxis in relation to intravenous arginine therapy, caution regarding medications such as remdesivir, and the incidence of gastrointestinal complications., (© 2021. Springer-Verlag GmbH Germany, part of Springer Nature.)

BACKGROUND The normalization of serum lactate levels in a patient with non-syndromic mitochondrial disorder due to the m.3243A>G mitochondrial DNA (mtDNA) variant has not been previously reported. CASE REPORT A 57-year-old woman was diagnosed with mitochondrial encephalopathy, lactic acidosis, and stroke-like episodes (MELAS) due to the m.3243A>G variant, with low heteroplasmy rates (31%), at age 50. The initial manifestations were short stature, migraine, and diabetes. With progression of the disease, multisystem involvement developed, affecting the brain (stroke-like episode, mild cognitive impairment), eyes (pigmentary retinopathy), ears and the vestibular system (impaired hearing, tinnitus, imbalance, drop attacks, vertigo), intestines (constipation, distended abdomen, gastro-esophageal reflux, gastroparesis), and the muscles (muscle weakness). The gastrointestinal involvement was most prominent and most significantly lowered the patient's quality of life. The diabetes was well controlled with an insulin pump. Recurrent, acute deteriorations responded favorably to L-arginine. Owing to lifestyle and diet changes 2 years after diagnosis (start of art classes, increase in spin biking to 22.5 km 3 times per week, travel to Hawaii, adherence to low-carbohydrate high-protein diet), the patient managed to lower elevated serum lactate levels to largely normal values. CONCLUSIONS Gastrointestinal compromise may be the prominent manifestation of the m.3243A>G variant, lifestyle and diet changes may lower serum lactate in m.3243A>G carriers, and low heteroplasmy rates of the m.3243A>G variant in scarcely affected tissues do not exclude pathogenicity.

Background: Mitochondrial encephalomyopathy, lactic acidosis and stroke-like episodes (MELAS) syndrome is a rare progressive disease with acute neurological episodes caused by a mitochondriopathy. Due to a defect of oxidative phosphorylation in the respiratory chain, there is impaired mitochondrial energy production with subsequent lactic acidosis, especially in situations with increased stress. Due to the high risk of metabolic derailment MELAS syndrome is a great challenge with respect to the perioperative management of anesthesia., Objective: This article gives a general overview of the special features of anesthesia management in patients with MELAS syndrome. A case report is presented in order to demonstrate how intraoperative parenteral nutrition can possibly be used to counteract the formation of lactic acidosis., Material and Methods: A systematic review of the literature was performed. As only very few reports on MELAS syndrome are available, a case report was also integrated into this overview article for illustration purposes., Results and Conclusion: Patients with MELAS syndrome represent a challenging cohort with respect to management of anesthesia and an intensive monitoring of the metabolic status is crucial. In cases of increasing lactate values, the administration of intraoperative parenteral nutrition seems to be a suitable approach to avoid lactic acidosis and to improve the perioperative treatment of patients with MELAS syndrome in the future.

Purpose of Review: We would like to inform clinicians that the systematic administration of oral and intravenous L-arginine is therapeutically beneficial and clinically useful for patients with mitochondrial myopathy, encephalopathy, lactic acidosis, and stroke-like episodes (MELAS), when they maintain plasma arginine concentration at least 168 μmol/l., Recent Findings: MELAS is associated with endothelial dysfunction by decreased plasma L-arginine, nitric oxide (NO), and cyclic guanosine monophosphate. Endothelial dysfunction is also evident using flow-mediated vasodilation measurement by high-resolution Doppler echocardiography in the forearm artery in patients with MELAS. L-arginine is known to be an important precursor of NO to normalize the endothelial function in MELAS. In our clinical trial followed by 7 years follow-up study, the systematic administration of L-arginine to patients with MELAS significantly improved the survival curve of patients compared with natural history. Maintaining plasma arginine concentration at least 168 μmol/l may prevent the ictuses through the putative pathophysiologic mechanism and optimal normalization of endothelial dysfunction., Summary: Neither death nor bedriddenness occurred during the 2-year clinical trials, and the latter did not develop during the 7-year follow-up despite the progressively neurodegenerative and eventually life-threatening nature of MELAS. Therapeutic regimen of L-arginine on MELAS may be beneficial and clinically useful for patient care with MELAS.

Wharton's jelly mesenchymal stem cells (WJMSCs) transfer healthy mitochondria to cells harboring a mitochondrial DNA (mtDNA) defect. Mitochondrial myopathy, encephalomyopathy, lactic acidosis, and stroke-like episodes (MELAS) is one of the major subgroups of mitochondrial diseases, caused by the mt.3243A>G point mutation in the mitochondrial tRNALeu (UUR) gene. The specific aim of the study is to investigate whether WJMSCs exert therapeutic effect for mitochondrial dysfunction in cells of MELAS patient through donating healthy mitochondria. We herein demonstrate that WJMSCs transfer healthy mitochondria into rotenone-stressed fibroblasts of a MELAS patient, thereby eliminating mutation burden and rescuing mitochondrial functions. In the coculture system in vitro study, WJMSCs transferred healthy mitochondria to rotenone-stressed MELAS fibroblasts. By inhibiting actin polymerization to block tunneling nanotubes (TNTs), the WJMSC-conducted mitochondrial transfer was abrogated. After mitochondrial transfer, the mt.3243A>G mutation burden of MELAS fibroblasts was reduced to an undetectable level, with long-term retention. Sequencing results confirmed that the transferred mitochondria were donated from WJMSCs. Furthermore, mitochondrial transfer of WJMSCs to MELAS fibroblasts improves mitochondrial functions and cellular performance, including protein translation of respiratory complexes, ROS overexpression, mitochondrial membrane potential, mitochondrial morphology and bioenergetics, cell proliferation, mitochondrion-dependent viability, and apoptotic resistance. This study demonstrates that WJMSCs exert bioenergetic therapeutic effects through mitochondrial transfer. This finding paves the way for the development of innovative treatments for MELAS and other mitochondrial diseases.

Stroke-like episodes (SLEs) are the hallmark of mitochondrial encephalopathy with lactic acidosis and stroke-like episode (MELAS) syndrome but rarely occur also in other specific or nonspecific mitochondrial disorders. Pathophysiologically, SLLs are most likely due to a regional disruption of the blood-brain barrier triggered by the underlying metabolic defect, epileptic activity, drugs, or other factors. SLEs manifest clinically with a plethora of cerebral manifestations, which not only include features typically seen in ischemic stroke, but also headache, epilepsy, ataxia, visual impairment, vomiting, and psychiatric abnormalities. The morphological correlate of a SLE is the stroke-like lesion (SLL), best visualised on multimodal MRI. In the acute stages, a SLL presents as vasogenic edema but may be mixed up with cytotoxic components. Additionally, SLLs are characterized by hyperperfusion on perfusion studies. In the chronic stage, SLLs present with a colorful picture before they completely disappear, or end up as white matter lesion, cyst, laminar cortical necrosis, focal atrophy, or as toenail sign. Treatment of SLLs is symptomatic and relies on recommendations by experts. Beneficial effects have been reported with nitric-oxide precursors, antiepileptic drugs, antioxidants, the ketogenic diet, and steroids. Lot of research is still needed to uncover the enigma SLE/SLL., (Copyright © 2019 Elsevier B.V. All rights reserved.)

The cell penetrating peptide, Pep-1, has been shown to facilitate cellular uptake of foreign mitochondria but further research is required to evaluate the use of Pep-1-mediated mitochondrial delivery (PMD) in treating mitochondrial defects. Presently, we sought to determine whether mitochondrial transplantation rescue mitochondrial function in a cybrid cell model of mitochondrial myopathy, encephalopathy, lactic acidosis, and stroke-like episodes (MELAS) disease. Following PMD, recipient cells had internalized donor mitochondria after 1 h, and expressed higher levels of normal mitochondrial DNA, particularly at the end of the treatment and 11 days later. After 4 days, mitochondrial respiratory function had recovered and biogenesis was evident in the Pep-1 and PMD groups, compared to the untreated MELAS group. However, only PMD was able to reverse the fusion-to-fission ratio of mitochondrial morphology, and mitochondria shaping proteins resembled the normal pattern seen in the control group. Cell survival following hydrogen peroxide-induced oxidative stress was also improved in the PMD group. Finally, we observed that PMD partially normalized cytokine expression, including that of interleukin (IL)-7, granulocyte macrophage-colony-stimulating factor (GM-CSF), and vascular endothelial growth factor (VEGF), in the MELAS cells. Presently, our data further confirm the protective effects of PMD as well in MELAS disease.

Mitochondrial disease is caused by a deficiency in the energy supply to cells due to mitochondrial dysfunction. Mitochondrial encephalomyopathy, lactic acidosis and stroke-like episodes (MELAS) is a mitochondrial disease that presents with stroke-like episodes such as acute onset of neurological deficits and characteristic imaging findings. Stroke-like episodes in MELAS have the following features: 1) neurological deficits due to localization of lesions in the brain, 2) episodes often accompany epilepsy, 3) lesions do not follow the vascular supply area, 4) lesions are more often seen in the posterior brain than in the anterior brain, 5) lesions spread to an adjacent area in the brain, and 6) neurological symptoms often disappear together with imaging findings, but later relapse. About 80% of patients with MELAS have an A-to-G transition mutation at the nucleotide pair 3243 in the dihydrouridine loop of mitochondrial tRNA Leu(UUR) , which causes the absence of posttranscriptional taurine modification at the wobble nucleotide of mitochondrial tRNA Leu(UUR) and disrupts protein synthesis. However, the precise pathophysiology of stroke-like episodes is under investigation, with possible hypotheses for these episodes including mitochondrial angiopathy, mitochondrial cytopathy, and neuron-astrocyte uncoupling. With regard to treatment, L-arginine and taurine have recently been suggested for relief of clinical symptoms.

We report the case of a mother and two children who shared a mitochondrial DNA A3243G mutation. The mother had diabetes mellitus, neurogenic bladder, bradykinesia, dystonia, and slowly progressive cerebellar ataxia. Her two daughters were diagnosed with mitochondrial myopathy, encephalopathy, lactic acidosis, and stroke-like episodes at adolescence. They all presented with gastrointestinal symptoms at an advanced clinical stage. They were diagnosed with chronic intestinal pseudo-obstruction, and they were resistant to therapy. The mother and her youngest daughter died from aspiration pneumonia because of vomiting. The determination of chronic intestinal pseudo-obstruction is an important prognostic factor in patients with the mitochondrial DNA A3243G variant.

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., (Copyright © 2016 Elsevier Inc. All rights reserved.)

Importance: Strokelike episodes are a cardinal feature of several mitochondrial syndromes, including mitochondrial encephalomyopathy, lactic acidosis, and strokelike episodes (MELAS). Recent advances in the understanding of the pathophysiologic mechanisms of strokelike episodes in MELAS have led to improved treatment options., Observations: Current understanding of the cause of strokelike episodes in MELAS and present recommendations to assist in the identification and treatment of patients with MELAS who present with stroke are presented. Mounting evidence points toward a benefit of the nitric oxide precursors, arginine, to both prevent and reduce the severity of strokes in patients with MELAS., Conclusions and Relevance: Although much information is still needed regarding the appropriate dosing and timing of arginine therapy in patients with MELAS, urgent administration of nitric oxide precursors in patients with MELAS ameliorates the clinical symptoms associated with strokelike episodes.

Importance: Stroke-like episodes signal progression and significant disability in the mitochondrial encephalomyopathy lactic acidosis and stroke-like episodes syndrome. Arginine is widely used as a treatment for stroke-like episode, although there is little evidence for this intervention. We discuss the management of a patient with mitochondrial encephalomyopathy lactic acidosis and stroke-like episodes who presented with a stroke-like episode., Observation: During a seizure, which triggers the stroke-like episode, neurons are forced to utilize glycolysis as a source of adenosine triphosphate. Glycolytic by-products are damaging to the neuron. Breakdown of the blood-brain barrier leads to vasogenic edema., Conclusion: Treatment of stroke-like episode should include anticonvulsants interictally to prevent seizures and dexamethasone ictally to help repair the blood-brain barrier., (Copyright © 2016 Elsevier Inc. All rights reserved.)

Mitochondrial encephalomyopathy, lactic acidosis, and strokelike episodes syndrome (MELAS) is a rare inherited mitochondrial disorder, commonly due to the m.3243A>G mutation, which typically presents with seizures, headaches, and acute neurological stroke-mimicking deficits. At onset, there is often no general intellectual deterioration in these patients, although specific cognitive deficits in peculiar language domains, visual construction, attention, abstraction, or flexibility may be present. To date, there is no evidence for an effective treatment in individuals with MELAS. Herein, we describe the case of young woman affected by MELAS who underwent an intensive cognitive training by means of the following methods: (a) traditional cognitive training, (b) computerized cognitive training (CCT), and (c) CCT plus a low-intensity aerobic motor exercise. We compared her cognitive and psychological profile at baseline (T0) and at the end of each training (i.e., (Time 1, Time 2, and Time 3 [T3]) using a proper psychometric battery, and we found a greater improvement at T3. Our findings support the idea that the combined CCT with motor training could represent a valuable therapeutic opportunity in MELAS.

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.

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., (Copyright © 2015 Elsevier Inc. All rights reserved.)

Mitochondrial diseases are a diverse group of inherited and acquired disorders that result in inadequate energy production. They can be caused by inheritable genetic mutations, acquired somatic mutations, and exposure to toxins (including some prescription medications). Normal mitochondrial physiology is responsible, in part, for the aging process itself, as free radical production within the mitochondria results in a lifetime burden of oxidative damage to DNA, especially the mitochondrial DNA that, in turn, replicate the mutational burden in future copies of itself, and lipid membranes. Primary mitochondrial diseases are those caused by mutations in genes that encode for mitochondrial structural and enzymatic proteins, and those proteins required for mitochondrial assembly and maintenance. A number of common adult maladies are associated with defective mitochondrial energy production and function, including diabetes, obesity, hyperthyroidism, hypothyroidism, and hyperlipidemia. Mitochondrial dysfunction has been demonstrated in many neurodegenerative disorders, including Alzheimer's disease, Parkinson disease, amyotrophic lateral sclerosis, and some cancers. Polymorphisms in mitochondrial DNA have been linked to disease susceptibility, including death from sepsis and survival after head injury. There is considerable overlap in symptoms caused by primary mitochondrial diseases and those illnesses that affect mitochondrial function, but are not caused by primary mutations, as well as disorders that mimic mitochondrial diseases, but are caused by other identified mutations. Evaluation of these disorders is complex, expensive, and not without false-negative and false-positive results that can mislead the physician. Most of the common heritable mitochondrial disorders have been well-described in the literature, but can be overlooked by many clinicians if they are uneducated about these disorders. In general, the evaluation of the classic mitochondrial disorders has become straightforward if the clinician recognized the phenotype and orders appropriate confirmatory testing. However, the majority of patients referred for a mitochondrial evaluation do not have a clear presentation that allows for rapid identification and testing. This article provides introductory comments on mitochondrial structure, physiology, and genetics, but will focus on the presentation and evaluation of adults with mitochondrial symptoms, but who may not have a primary mitochondrial disease.

Mitochondrial diseases are a significant part of neuromuscular diseases. Majority of them is multisystemic disorder. The diagnosis can be established in more and more cases. Beyond the routine neurological examination imaging methods (MRI and MR-spectroscopy) and electrophysiology (EMG, ENG, EEG, evoked potential tests) might be helpful in setting the diagnosis. Raised blood lactate level supports the diagnosis. Muscle biopsy demonstrates mitochondrial abnormalities in the majority of cases. The positivity of genetic tests is low, because the amount of mitochondrial DNA alterations is different in tissues. Therefore other tissue than blood (mainly muscle) is necessary for genetic tests. The other reason is that the respiratory chain is under double -mitochondrial and nuclear - genetic control, and testing the nuclear genes are available only in selected laboratories. The treatment is limited, mainly symptomatic.

Mitochondrial respiratory chain disorders are relatively common inborn errors of energy metabolism, with a combined prevalence of one in 5000. These disorders typically affect tissues with high energy requirements, and cerebral involvement occurs frequently in childhood, often manifesting in seizures. Mitochondrial diseases are genetically heterogeneous; to date, mutations have been reported in all 37 mitochondrially encoded genes and more than 80 nuclear genes. The major genetic causes of mitochondrial epilepsy are mitochondrial DNA mutations (including those typically associated with the mitochondrial encephalomyopathy, lactic acidosis, and stroke-like episodes [MELAS] and myoclonic epilepsy with ragged red fibres [MERRF] syndromes); mutations in POLG (classically associated with Alpers syndrome but also presenting as the mitochondrial recessive ataxia syndrome [MIRAS], spinocerebellar ataxia with epilepsy [SCAE], and myoclonus, epilepsy, myopathy, sensory ataxia [MEMSA] syndromes in older individuals) and other disorders of mitochondrial DNA maintenance; complex I deficiency; disorders of coenzyme Q(10) biosynthesis; and disorders of mitochondrial translation such as RARS2 mutations. It is not clear why some genetic defects, but not others, are particularly associated with seizures. Epilepsy may be the presenting feature of mitochondrial disease but is often part of a multisystem clinical presentation. Mitochondrial epilepsy may be very difficult to manage, and is often a poor prognostic feature. At present there are no curative treatments for mitochondrial disease. Individuals with mitochondrial epilepsy are frequently prescribed multiple anticonvulsants, and the role of vitamins and other nutritional supplements and the ketogenic diet remain unproven., (© The Author. Developmental Medicine & Child Neurology © 2012 Mac Keith Press.)

Mitochondrial myopathy, encephalopathy, lactic acidosis, and stroke-like episodes (MELAS) is a maternally inherited multisystem mitochondrial disorder. Although many molecular and cellular mechanisms have been discovered leading to mitochondrial cytopathy, the pathogenic mechanism of stroke-like episodes seen in MELAS has not been clarified yet. According to the muscle and brain pathology and vascular physiology, mitochondrial angiopathy, or endothelial dysfunction, were proposed to play an important role for developing stroke-like episodes. Based on a hypothesis of mitochondrial angiopathy theory, we use L-arginine in MELAS patients and report its usefulness. This review aims to give a general idea on the actual knowledge about the possible pathogenic mechanism of stroke-like episodes, including clinical symptoms that lead to stroke-like episodes, muscle, or brain pathology, molecular cellular functions, neuroimagings including MRI, MRS, and SPECT, and the proposed site of action of L-arginine therapy on MELAS patients. Currently, L-arginine therapy may be the most promising for the treatment of stroke-like episodes in MELAS.

Mitochondrial encephalomyopathy, lactic acidosis, and stroke (MELAS) syndrome is a mitochondrial genetic disorder caused by a point mutation, resulting in the substitution of guanine for adenine at nucleotide 3243 (A3243G) of mitochondrial DNA. This disease is characterized by a multisystem disorder with variable manifestations. The authors review heart involvement in this disease.

Mitochondrial encephalomyopathy, lactacidosis and stroke-like episode (MELAS) syndrome is a phenotypically and genetically heterogeneous mitochondrial disorder with a clinical onset between the first and third decade. The clinical hallmark is the stroke-like-episode, which mimicks ischemic stroke but is usually transient and non-disabling in nature. The morphological equivalent on MRI is a T2-hyperintensity, predominantly over the temporo-parieto-occipital region, not confined to a vascular territory, which is also hyperintense on diffusion weighted imaging and on apparent diffusion coefficient sequences (vasogenic edema, stroke-like lesion). Additional features include seizures, cognitive decline, psychosis, lactic acidosis, migraine, visual impairment, hearing loss, short stature, diabetes, or myopathy. Muscle biopsy typically shows ragged-red fibers, COX-negative fibers, SDH hyperreactivity, and abnormally shaped mitochondria with paracristalline inclusions. The diagnosis is confirmed by demonstration of a biochemical respiratory chain defect or one of the disease-causing mutations, of which 80 % affect the mitochondrial tRNALeu gene.

Mitochondrial myopathy, encephalopathy, lactic acidosis, and stroke-like episodes (MELAS) is a distinct clinical syndrome caused by mutations in mitochondrial DNA. Crucial molecular mechanism includes a lack of taurine modification at the wobble uridine of the mutant tRNA(Leu(UUR)), causing UUG condon-specific translational defect and mitochondrial protein synthesis failure. However, the pathogenesis of stroke-like episodes remains unknown. We previously reported that stroke-like episodes were more likely non-ischemic events, characterized by increased capillary permeability, hyperperfusion, neuronal vulnerability and neuronal hyperexcitability, in which neuronal hyperexcitability plays an important role in initiation of the cascades of stroke-like events by increasing energy demand. We also emphasized a role of prolonged epileptic activities in progressive spread of stroke-like lesions, and then proposed a non-ischemic neurovascular cellular mechanism. Once neuronal hyperexcitability developed in a localized region as a result from either mitochondrial dysfunction in capillary endothelial cells, or in neurons or astrocytes, epileptic activities depolarize adjacent neurons, leading to propagation of epileptic activities in surrounding cortex. Increased capillary permeability in the presence of mitochondrial capillary angiopathy may cause unique edematous lesions predominantly involving the cortex. As a consequence, most susceptible layers of the cortex may result in neuronal loss. Therapeutic targets include each ongoing process of the disease.

Mitochondria are semiautonomous cell organelles which possess their own genome (mtDNA) but nonetheless depend on the import of nuclear-encoded proteins. In recent years, several mutations of mtDNA have been associated with specific diseases of the muscles and nervous system. In 1993, the A>G point mutation at position 3243 of the mtDNA, until then a prominent genetic marker for mitochondrial encephalomyopathy, lactic acidosis, and stroke-like episodes (MELAS), was detected in patients with progressive external ophthalmoplegia (PEO). Due to the divergent clinical presentations of MELAS and PEO, the presence of potential nuclear secondary mutations or so-called modifier genes had been suspected. Now it is well known that a bidirectional information flow between the mitochondrion and the cell nucleus exists and that nuclear gene expression adapts to the functional status of the mitochondria. However it remains unclear when and how the nucleus responds to changes or mutations of the mtDNA and if there are indeed disease-specific biomarker genes whose expression changes in case of mtDNA aberrations. This review article focuses on the most recent gene expression profiling studies in the field of classic mitochondrial disorders.

Objectives: We sought to determine the clinical spectrum, survival, and long-term functional outcome of a cohort of pediatric patients with mitochondrial diseases and to identify prognostic factors., Methods: Medical charts were reviewed for 73 children diagnosed between 1985 and 2005. The functional status of living patients was assessed prospectively by using the standardized Functional Independence Measure scales., Results: Patients fell into 7 phenotypic categories: neonatal-onset lactic acidosis (10%), Leigh syndrome (18%), nonspecific encephalopathy (32%), mitochondrial (encephalo)myopathy (19%), intermittent neurologic (5%), visceral (11%), and Leber hereditary optic neuropathy (5%). Age at first symptoms ranged from prenatal to 16 years (median: 7 months). Neurologic symptoms were the most common (90%). Visceral involvement was observed in 29% of the patients. A biochemical or molecular diagnosis was identified for 81% of the patients as follows: deficiency of complex IV (27%), of pyruvate dehydrogenase or complex I (25% each), of multiple complexes (13%), and of pyruvate carboxylase (5%) or complexes II+III (5%). A mitochondrial DNA mutation was found in 20% of patients. At present, 46% of patients have died (median age: 13 months), 80% of whom were <3 years of age. Multivariate analysis showed that age at first symptoms was a major independent predictor of mortality: patients with first symptoms before 6 months had a highly increased risk of mortality. Cardiac or visceral involvement and neurologic crises were not independent prognostic factors. Living patients showed a wide range of independence levels that correlated positively with age at first symptoms. Among patients aged >5 years (n = 32), 62% had Functional Independence Measure quotients of >0.75., Conclusions: Mitochondrial diseases in children span a wide range of symptoms and severities. Age at first symptoms is the strongest predictor mortality. Despite a high mortality rate in the cohort, 62% of patients aged >5 years have only mild impairment or normal functional outcome.

Mitochondrial encephalomyopathies are a multisystemic group of disorders that are characterised by a wide range of biochemical and genetic mitochondrial defects and variable modes of inheritance. Among this group of disorders, the mitochondrial myopathy, encephalopathy, lactic acidosis with stroke-like episodes (MELAS) syndrome is one of the most frequently occurring, maternally inherited mitochondrial disorders. As the name implies, stroke-like episodes are the defining feature of the MELAS syndrome, often occurring before the age of 15 years. The clinical course of this disorder is highly variable, ranging from asymptomatic, with normal early development, to progressive muscle weakness, lactic acidosis, cognitive dysfunction, seizures, stroke-like episodes, encephalopathy and premature death. This syndrome is associated with a number of point mutations in the mitochondrial DNA, with over 80% of the mutations occurring in the dihydrouridine loop of the mitochondrial transfer RNA(Leu(UUR)) [tRNA(Leu)((UUR))] gene. The pathophysiology of the disease is not completely understood; however, several different mechanisms are proposed to contribute to this disease. These include decreased aminoacylation of mitochondrial tRNA, resulting in decreased mitochondrial protein synthesis; changes in calcium homeostasis; and alterations in nitric oxide metabolism. Currently, no consensus criteria exist for treating the MELAS syndrome or mitochondrial dysfunction in other diseases. Many of the therapeutic strategies used have been adopted as the result of isolated case reports or limited clinical studies that have included a heterogeneous population of patients with the MELAS syndrome, other defects in oxidative phosphorylation or lactic acidosis due to disorders of pyruvate metabolism. Current approaches to the treatment of the MELAS syndrome are based on the use of antioxidants, respiratory chain substrates and cofactors in the form of vitamins; however, no consistent benefits have been observed with these treatments.

Mitochondrial myopathy, encephalopathy, lactic acidosis and stroke-like episodes (MELAS) is the most common maternally inherited mitochondrial disease. An A-->G mutation in the transfer RNA(Leu(UUR)) gene at position 3243 of the mitochondrial DNA accounts for most MELAS cases. The transient nature of the stroke-like episodes is reflected in abnormalities on neuroimaging. The cardinal laboratory abnormalities include elevated serum lactate during the acute episodes and respiratory enzyme defects in skeletal muscle. Muscle biopsy also helps confirm the diagnosis by identifying abnormal proliferation of mitochondria. Although current treatment options for MELAS are largely supportive, several therapeutic approaches have been attempted with limited success. Genetic counseling is an important component of patient management in MELAS. Newer reproductive technologies hold promise for reducing the recurrence of MELAS in subsequent generations. Advances in research into gene therapy offer hope of treatment for the future.

Introduction: Mitochondrial myopathy, encephalopathy, lactic acidosis and stroke-like episodes (MELAS) is a rare, neurodegenerative and fatal disease caused by mutations in the mitochondrial DNA. Multiple systems of the body, including the oral cavity, can be affected by this disease. An electronic search of Medline spanning the years 1985 to 2003 was carried out using the key words "MELAS, Dentistry." It yielded no literature on the dental aspects of MELAS., Clinical Picture: This report documents the case of a 6-year-old Chinese boy diagnosed with MELAS and highlights problems encountered in the multidisciplinary management of MELAS patients, including its dental management., Treatment and Outcome: Dental management was successfully performed under general anaesthesia with close medical supervision by paediatrician and anaesthetist., Conclusions: There is no known treatment of the underlying disease and the clinical course is usually unpredictable. Preventive dental care is important in this group of patients as concurrent medical conditions can complicate dental care.

The mitochondrial myopathy, encephalopathy, lactic acidosis and stroke-like episodes (MELAS) syndrome is a rare congenital disorder of mitochondrial DNA (mt-DNA). Patients with this syndrome may present to the otolaryngologist with sensorineural hearing loss (SNHL), which is genetic in origin. A high index of suspicion is required because this hearing loss is part of a syndrome for which early diagnosis and intervention is required.

Disorders of mitochondrial DNA (mtDNA) may commonly present to primary care physicians but go undiagnosed. A 36-year-old man with a 15-year history of psychosis, seizures, and sensorineural hearing loss and a family history of diabetes mellitus and heart disease presented to our hospital without a unifying diagnosis. Physiologic, biochemical, and genetic testing revealed deficient aerobic metabolism, a defect in mitochondrial electron transport, and the presence of an A-to-G point mutation at position 3243 of the mitochondrial leucine-transfer RNA gene, establishing the diagnosis of mitochondrial encephalopathy, lactic acidosis, and strokelike syndrome (MELAS). Diagnosing mtDNA disorders requires a careful integration of clinical signs and symptoms with pedigree analysis and multidisciplinary testing. Diagnosis is important to provide genetic counseling, avoid unnecessary evaluation, and facilitate therapy for symptomatic relief.

Defects of the mitochondrial energy production cab be expressed in many tissues and may lead to various types of diseases. Since defects can occur on many sites of the oxidative phosphorylation system, molecular diagnosis can be difficult. In typical mitochondrial syndromes, like MELAS- or MERRF-syndrome, diagnosis can be suspected already on clinical grounds. Lactate measured in various body fluids is still the best selective screening parameter. Loading tests, respectively ergometry is only necessary in the milder clinical forms of diseases or possibly in older children. The in vivo lactate determination e.g. In the CNS by 1H NMR spectroscopy can be helpful in evaluating prognosis. The diagnosis of a mitochondriopathy is usually confirmed enzymatically by tissue biopsies; skeletal muscle is still the tissue of the first choice because some enzyme deficiencies are not sufficiently expressed in cultured fibroblasts. If possible, intact mitochondria should be investigated polarografically along with histology and histochemistry. Finally several parts of the respiratory chain and pyruvate dehydrogenase complex are analyzed by single enzyme measurement. Also combined deficiencies have been described. Polypeptide subunits of respiratory chain complexes can be investigated by means of immunoblotting. The investigations of the mitochondrial DNA from the end of the diagnostic scale. The application of various new therapeutic agents, such as antioxidants, radical scavangers and cofactors have not come to any persuasive clinical result. But there is a number of reports about some successful treatment with coenzyme Q10, vitamin K3, vitamin C, riboflavin, thiamine, dichloroacetate and in PDHC -deficiency with ketogenic diet. Mitochondrial gene therapy appears only theoretical and speculative. Because of the enormous heterogeneity even on the DNA-level genetic counselling is reserved for some cases with exact molecular diagnosis.

Long-term home mechanical ventilation of children has only recently become more practically feasible and ethically acceptable by the medical community. It has been particularly controversial in cases of degenerative myopathies in which quality of life has been questioned. There are no reports in the literature of long-term home mechanical ventilation of a child with mitochondrial encephalomyopathy (MELAS) syndrome despite the many descriptions of possible etiologies of the concomitant respiratory failure. The patient reported here has used home mechanical ventilation for 6 years with few medical complications, no hospitalizations in the past 3 years, and increased function in activities of daily living. Despite the ill-defined nature of the disease and uncertain prognosis, we believe that long-term home mechanical ventilation of children with early onset MELAS syndrome is a viable option for both patients and their families and results in overall improvement in quality of life for the patient.

Metabolic myopathies are subdivided into disturbances of anaerobic cytoplasmic and aerobic mitochondrial metabolism. With the exception of carnitine deficiency these myopathies are based on enzymopathies. Since gene therapy is not yet available no causal therapy is possible. This paper discusses possibilities for symptomatic therapy. Good results are found with carnitine substitution. Enzymopathies can be improved by using other metabolic pathways or by addition of co-factors of the impaired pathways. This leads to a reduction of myalgia, cramps, and endurance exercise intolerance.