A case report of late-onset MELAS with paroxysmal sympathetic hyperactivity syndrome / 中华神经科杂志

Paroxysmal sympathetic hyperactivity (PSH) is a syndrome characterized by paroxysmal tachycardia, increased blood pressure, tachypnea, hyperthermia, profuse sweating, abnormal posture or dystonia. It occurs in diseases such as moderate to severe brain injury, cerebral hypoxia, hydrocephalus, brain tumor and encephalitis. At present, the etiology and pathogenesis are still unclear, and it is easy to be misdiagnosed as epilepsy clinically. This article reports a 43-year-old male patient with late-onset mitochondrial encephalomyopathy, lactic acidosis and stroke-like episodes (MELAS) confirmed by genetic testing. During hospitalization, he suddenly developed episodic involuntary limb movements, profuse sweating, tachycardia, and arterial hypertension. He was initially diagnosed with symptomatic epilepsy, but long-term electroencephalogram monitoring showed no synchronized discharge, and he was given antiepileptic drugs. The treatment was also ineffective. Brain magnetic resonance imaging revealed a new lesion in the left insular and insular operculum. Dexmedetomidine, baclofen, and gabapentin were given to suppress sympathetic nerve excitability. Drugs were effective, so the diagnosis was corrected to PSH. There is no report of MELAS complicated with PSH in the previous literature. It is speculated that it may be related to the low clinical cognition of PSH. In this case, new lesions in the insula and insular operculum appeared during the onset of PSH, suggesting that may be related to the pathogenesis of PSH.

A case of mitochondrial myopathy, encephalopathy, lactic acidosis and stroke-like episodes mimicking migraine attacks with visual aura / 中国医师杂志

Objective:To study the case of mitochondrial myopathy, encephalopathy, lactic acidosis and stroke-like episodes (MELAS) which mimic migraine attacks with visual aura, to analyze the clinical features, and to recognize the nature of headache.Methods:The clinical features, image data and video electroencephalogram (EEG) of a suspected patient with MELAS were analyzed. Genomic DNA of mitochondria was extracted from blood and the next generation sequencing was performed to explore the mutation of genes about MELAS.Results:The patient was adolescent-onset, and presented with migraine-like attacks with visual aura, epileptic seizures, stroke-like episodes and hyperlactemia. Brain images suggested basal ganglia calcification, reversible left occipital cortex infarction and abnormal lactic acid peaks in both occipital cortex. Video EEG suggested abnormal adolescent EEG. Mitochondrial DNA sequencing showed that MT-TL1 gene had m. 3243A>G pathogenic mutation.Conclusions:There are a variety of clinical manifestations in MELAS, and migraine-like attacks with visual aura as initial symptoms may be manifestations of occipital lobe epilepsy. Clinicians should avoid confusing the diagnosis of migraine with visual aura, occipital epilepsy and MELAS, in order to make rational clinical decisions.

Síndrome MELAS en pediatría. Reporte de caso / MELAS Syndrome in pediatrics. Case report

Resumen Introducción. El síndrome de encefalopatía mitocondrial, acidosis láctica y episodios similares a un accidente cerebrovascular (MELAS, por su sigla en inglés) es una de las enfermedades mitocondriales más frecuentes. Estas patologías se caracterizan por ser hereditarias, multisistémicas y progresivas, y por causar un compromiso predominantemente neurológico que provoca discapacidad y mortalidad, por lo que el diagnóstico temprano y la consejería genética son de gran importancia para mejorar el pronóstico de estos pacientes. Presentación del caso. Paciente femenina de cinco años quien fue llevada a consulta al servicio de pediatría por convulsión y ataxia, y en quien se evidenció retraso psicomotor. Aunque los estudios de neuroimagen fueron normales, se observó hiperlactatemia. Se encontró una relación lactato/piruvato >20, por lo que se sospechó enfermedad mitocondrial. Seis meses después, la paciente presentó deterioro neurológico progresivo caracterizado por alteración de la consciencia, mioclonías y hemiparesia. Se realizó tomografía axial computarizada de cráneo y resonancia magnética por espectroscopia que permitieron identificar una lesión isquémica occipital y aumento del lactato cerebral, respectivamente. Para confirmar el diagnóstico de síndrome MELAS, se solicitó estudio de ADN mitocondrial, en el que se observó la mutación m.3243A>G en el gen MT-TL1. La paciente tuvo un rápido deterioro, presentando una involución de las capacidades adquiridas, falleciendo a los cuatro años del inicio de los signos clínicos. Conclusión. Las enfermedades mitocondriales deben ser consideradas en pacientes con antecedentes de epilepsia y otras alteraciones neurológicas como ataxia e involución del neurodesarrollo.

Abstract Introduction: MELAS (mitochondrial myopathy, encephalopathy, lactic acidosis, and stroke) syndrome is the most common mitochondrial disease. These diseases are hereditary, multi-systemic and progressive, and lead to a predominant neurological involvement that causes disability and death, so early diagnosis and genetic counseling are of great importance for improving the prognosis of these patients. Case presentation: Five-year-old female patient who was taken to the pediatrics service of the hospital due to epileptic seizure, psychomotor retardation and ataxia. Although in the first medical consultation her neuroimaging studies were normal, hyperlactatemia was identified. In addition, a lactate to pyruvate ratio >20 was observed, so a mitochondrial disease was suspected. Six months later, the patient showed progressive deterioration of her health condition. A cranial CT scan and a magnetic resonance spectroscopy allowed the identification of an ischemic lesion in the occipital lobe and increased cerebral lactate levels, respectively. In order to confirm the MELAS syndrome diagnosis, a mitochondrial DNA study was requested, in which the m.3243A>G mutation was found. Unfortunately, the patient had a rapid deterioration of her health condition, showing a regression of her acquired functions, and died four years after the onset of the clinical signs. Conclusion: Mitochondrial diseases diagnosis should always be considered in patients with a history of epilepsy and other neurological disorders such as ataxia and neurodevelopmental regression.

Mitochondrial encephalopathy, lactic acidosis and stroke-like episodes / myoclonus epilepsy with ragged-red fibers /Leigh overlap syndrome caused by mitochondrial DNA 8344A>G mutation / 北京大学学报(医学版)

OBJECTIVE@#Mitochondrial deoxyribonucleic acid (mtDNA) 8344 A>G (m.8344A>G) mutation is the common mutation associated with mitochondrial myoclonus epilepsy with ragged-red fibers (MERRF) syndrome. Herein we report a rare case with mitochondrial encephalopathy, lactic acidosis and stroke-like episodes/MERRF/Leigh (MELAS/MERRF/Leigh) overlap syndrome caused by m.8344A>G mutation.@*METHODS@#The clinical and imaging data of the patient were collected and an open muscle biopsy was carried out. We further employed molecular genetic analyses to detect mtDNA mutation in the proband and his mother. And then a clinical and neuroimaging follow-up was performed.@*RESULTS@#This patient was a 25-year-old male, who developed exercise intolerance since the age of 6. At age 10, he suffered from acute episodes of hemianopia, and cranial magnetic resonance imaging (MRI) showed occipital stroke-like lesions and cranial magnetic resonance spectroscopy (MRS) revealed a lactate peak corresponding to the lesion. After that the patient presented slowly progressive psychomotor decline. He had myoclonic seizures and cerebellar ataxia since the age of 12. At age 21, he was admitted to our hospital because of confusion and cranial MRI revealed symmetrical lesions in bilateral posterior putamen, thalami and midbrain. Then repeated MRI showed progression of original lesions and new frontal multiple stroke-like lesions. Symptomatic and rehabilitation treatment relieved his condition. Follow-up cranial MRI at age 24 showed the lesions in basal ganglia and thalami diminished, and the midbrain lesions even completely vanished. Muscle pathology indicated the presence of numerous scattered ragged-red fibers (RRF), suggestive of a mitochondrial disorder. Polymerase chain reaction-restricted fragment length polymorphism (PCR-RFLP) detected the m.8344A>G mutation of the MT-TK gene encoding mitochondrial transfer RNA for lysine in the patient's blood. Next generation sequencing (NGS) of the whole mitochondrial genome identified that the proportion of m.8344A>G was 90%, and no other mtDNA mutation was detected. Sanger sequencing further identified this mutation both in the proband and his mother's blood, although the mutation load was much lower in his mother's blood with approximately 10% heteroplasmy.@*CONCLUSION@#The present study is the first to describe a patient with m.8344A>G mutation in association with the MELAS/MERRF/Leigh overlap syndrome, which expands the phenotypic spectrum of the m.8344A>G mutation.

The Usefulness of Muscle Biopsy in Initial Diagnostic Evaluation of Mitochondrial Encephalomyopathy, Lactic Acidosis, and Stroke-Like Episodes

PURPOSE: The disease entity mitochondrial encephalomyopathy, lactic acidosis, and stroke-like episodes (MELAS) is characterized by an early onset of stroke-like episodes. MELAS is the most dominant subtype of mitochondrial disease. Molecular genetic testing is important in the diagnosis of MELAS. The mitochondrial DNA (mtDNA) 3243A>G mutation is found in 80% of MELAS patients. Nevertheless, molecular analysis alone may be insufficient to diagnose MELAS because of mtDNA heteroplasmy. This study aimed to evaluate whether muscle biopsy is useful in MELAS patients as an initial diagnostic evaluation method. MATERIALS AND METHODS: The medical records of patients who were diagnosed with MELAS at the Department of Pediatrics of Gangnam Severance Hospital between January 2006 and January 2017 were reviewed. The study population included 12 patients. They were divided into two subgroups according to whether the results of muscle pathology were in accordance with mitochondrial diseases. Clinical variables, diagnostic evaluations, and clinical outcomes were compared between the two groups. RESULTS: Of the 12 patients, seven were muscle pathology-positive for mitochondrial disease. No statistically significant difference in clinical data was observed between the groups that were muscle pathology-positive and muscle pathology-negative for mtDNA 3243A>G mutation. Additionally, the patients with weakness as the initial symptom were all muscle pathology-positive. CONCLUSION: The usefulness of muscle biopsy appears to be limited to an initial confirmative diagnostic evaluation of MELAS. Muscle biopsy can provide some information in MELAS patients with weakness not confirmed by genetic testing.

Dexmedetomidine as a non-triggering anesthetic agent in a patient with MELAS syndrome and systemic sepsis: A case report

BACKGROUND: The selection of anesthetic agents is important in mitochondrial myopathy, encephalopathy, lactic acidosis, and stroke-like episodes (MELAS) syndrome patient because serious and unexpected complications can occur after anesthetic exposure.CASE: A 30-year-old man with MELAS syndrome and sepsis underwent colectomy. Propofol was administered by step-wise until target effect-site concentration (Ce) 1.0 µg/ml and stopped for the loss of consciousness and to avoid hemodynamic instability. After the loss of consciousness, total intravenous anesthesia (TIVA) using dexmedetomidine (1.0 µg/ml/h) and remifentanil (1–4 ng/ml of Ce) was performed for the maintenance of anesthesia to avoid malignant hyperthermia and mitochondrial dysfunction. During the surgery, the bispectral index score stayed between 26 and 44, and increased to 97 after the end of anesthesia.CONCLUSIONS: TIVA with dexmedetomidine and remifentanil as non-triggering anesthetic agents in patients with MELAS syndrome and systemic sepsis may have advantages to decrease damages associated with mitochondrial stress and metabolic burden.

Twenty-one-year follow-up of variable onset MELAS syndrome with heteroplasmic nt3243A>G mtDNA mutation: A case report

Mitochondrial encephalomyopathy, lactic acidosis, and stroke-like episodes (MELAS) syndrome is a maternally inherited mitochondrial disorder of which m.3243A>G is the most commonly associated mutation, resulting in an inability to meet the energy requirements of various organs. MELAS poses a diagnostic challenge owing to its multiple organ involvement and great clinical variability due to its heteroplasmic nature. We report three cases from a family who were initially misdiagnosed with myasthenia gravis or undiagnosed. Although there is no optimal consensus treatment approach for patients with MELAS because of the disease's heterogeneity, our 21-year-long therapy regimen of l-arginine, l-carnitine, and coenzyme Q10 supplementation combined with dietary management appeared to provide noticeable protection from the symptoms and complications. Prompt early diagnosis is important, as optimal multidisciplinary management and early intervention may improve outcomes.

Atypical Radiologic Manifestation of NARP Mimicking MELAS: a Case Report

Neurogenic weakness, ataxia and retinitis pigmentosa (NARP) syndrome is a rare maternally inherited mitochondrial disorder. Radiologic findings in NARP syndrome are varied; they include cerebral and cerebellar atrophy, basal ganglia abnormalities, and on rare occasions, leukoencephalopathy. This article describes an extremely rare case of NARP syndrome mimicking mitochondrial encephalomyopathy, lactic acidosis, and stroke-like episodes (MELAS).

A clinical and natural history research on mitochondrial encephalomyopathy, lactic acidosis and stroke-like episodes / 中华神经科杂志

Objective To summarize the clinical features,natural history and causes of death of mitochondrial encephalomyopathy,lactic acidosis and stroke-like episodes (MELAS).Methods We retrospectively evaluated the clinical findings of 64 patients diagnosed as MELAS more than 3 years (death cases excluded) in Huashan Hospital from January 2005 to March 2017 and analyzed the natural course and the causes of death of the disease.Results Among 64 patients,the male-to-female ratio was 1.3 ∶ 1.Median onset age was 20.5 (16.8) years.The peak of incidence age was from 14 to 22 years.The most common features of MELAS in acute phase were seizures (48/64,75.0％),headache (41/64,64.1％),blurred vision (37/64,57.8％),nausea and vomiting (27/64,42.1％),fever (25/64,39.1％),mental and behavioral disorder (24/64,37.5％).Lactate dehydrogenase (31/60,51.6％),resting blood lactic acid (43/58,74.1％) and cerebral spinal fluid lactic acid (9/9) were elevated.Abnormal findings in electroencephalogram (36/40,90.0％),electrocardiogram (37/47,78.7％),electromyography (25/41,61.0％) were detected.In this cohort,20 patients (20/64,31.3％) with MELAS were dead.A Kaplan-Meier survival curve showed the estimated overall median survival time was 12 years.The median survival time of the group onset before sex maturity (≤ 14 years) was 8 years and that in the group onset after sex maturity (＞ 14 years) was 21 years.The causes of death were cardiogenic incidence (4/20,20.0％),pulmonary infection (4/20,20.0％),lactic acidosis (2/20,10.0％) and status epilepticus (2/20,10.0％).Conclusions MELAS is usually presented in young people associated with high mortality rate.The leading causes of death are cardiogenic,pulmonary infection and lactic acidosis.

Effects and Mechanisms of Taurine as a Therapeutic Agent

Taurine is an abundant, β-amino acid with diverse cytoprotective activity. In some species, taurine is an essential nutrient but in man it is considered a semi-essential nutrient, although cells lacking taurine show major pathology. These findings have spurred interest in the potential use of taurine as a therapeutic agent. The discovery that taurine is an effective therapy against congestive heart failure led to the study of taurine as a therapeutic agent against other disease conditions. Today, taurine has been approved for the treatment of congestive heart failure in Japan and shows promise in the treatment of several other diseases. The present review summarizes studies supporting a role of taurine in the treatment of diseases of muscle, the central nervous system, and the cardiovascular system. In addition, taurine is extremely effective in the treatment of the mitochondrial disease, mitochondrial encephalopathy, lactic acidosis, and stroke-like episodes (MELAS), and offers a new approach for the treatment of metabolic diseases, such as diabetes, and inflammatory diseases, such as arthritis. The review also addresses the functions of taurine (regulation of antioxidation, energy metabolism, gene expression, ER stress, neuromodulation, quality control and calcium homeostasis) underlying these therapeutic actions.

Targeted elimination of mutant mitochondrial DNA in MELAS-iPSCs by mitoTALENs

Mitochondrial diseases are maternally inherited heterogeneous disorders that are primarily caused by mitochondrial DNA (mtDNA) mutations. Depending on the ratio of mutant to wild-type mtDNA, known as heteroplasmy, mitochondrial defects can result in a wide spectrum of clinical manifestations. Mitochondria-targeted endonucleases provide an alternative avenue for treating mitochondrial disorders via targeted destruction of the mutant mtDNA and induction of heteroplasmic shifting. Here, we generated mitochondrial disease patient-specific induced pluripotent stem cells (MiPSCs) that harbored a high proportion of m.3243A>G mtDNA mutations and caused mitochondrial encephalomyopathy and stroke-like episodes (MELAS). We engineered mitochondrial-targeted transcription activator-like effector nucleases (mitoTALENs) and successfully eliminated the m.3243A>G mutation in MiPSCs. Off-target mutagenesis was not detected in the targeted MiPSC clones. Utilizing a dual fluorescence iPSC reporter cell line expressing a 3243G mutant mtDNA sequence in the nuclear genome, mitoTALENs displayed a significantly limited ability to target the nuclear genome compared with nuclear-localized TALENs. Moreover, genetically rescued MiPSCs displayed normal mitochondrial respiration and energy production. Moreover, neuronal progenitor cells differentiated from the rescued MiPSCs also demonstrated normal metabolic profiles. Furthermore, we successfully achieved reduction in the human m.3243A>G mtDNA mutation in porcine oocytes via injection of mitoTALEN mRNA. Our study shows the great potential for using mitoTALENs for specific targeting of mutant mtDNA both in iPSCs and mammalian oocytes, which not only provides a new avenue for studying mitochondrial biology and disease but also suggests a potential therapeutic approach for the treatment of mitochondrial disease, as well as the prevention of germline transmission of mutant mtDNA.

Hallazgos radiológicos en sistema nervioso central (SNC) del síndrome de MELAS: reporte de caso / Radiological findings of MELAS syndrome in central nervous system (CNS): case report

RESUMEN Presentamos el caso clínico de una paciente adulta joven con episodios recurrentes sugestivos de ataque cerebrovascular, con cambios radiológicos típicos de enfermedad de MELAS con confirmación genética de mutación en el gen A3243G.

SUMMARY A clinical case of a young adult patient with recurrent episodes suggestive of stroke, with typical radiological changes of MELAS disease with genetic confirmation of mutation in A3243G gene.

Clinical, myopathological and genetic research of a patient with mitochondrial encephalomyopathy, lactic acidosis and stroke-like episodes/Leigh syndrome overlap syndrome caused by m.10158 T>C mutation / 中华神经科杂志

Objective To report the clinical, myopathological and genetic features of a patient with mitochondrial encephalomyopathy, lactic acidosis and stroke-like episodes (MELAS)/Leigh syndrome (LS) overlap syndrome who carried m.10158 T>C mutation. Methods The patient′s clinical and imaging materials were collected. An open biopsy of right biceps brachii was performed. DNA samples were prepared from the patient and her mother′s blood. Direct sequencing of the complete mitochondrial genome was performed to detect the mtDNA mutation.Western blotting was used to estimate the content of respiratory complexes in the patient′s muscle. Results The patient was a 40-year-old female. She had seizures and lost consciousness for 9 months. Brain MRI findings consisted of asymmetrical lesions in the cerebral cortex of the frontal and temporal lobes, as well as symmetrical lesions bilaterally in the basal ganglia. Muscle biopsy showed typical ragged red fibers. Direct sequencing of the complete mitochondrial genome from blood and muscle of the patient revealed the T-to-C transition at nucleotide position 10158 in the MT-ND3 gene.The mutation rate was 9.31% and 70.0%, respectively.Western blotting demonstrated that the contents of complexes Ⅰ and Ⅳ were significantly lower in the patient′s muscle mitochondria compared with the normal controls (53.1%±1.2% vs 88.6%±1.7%, t=4.08, PC mutation in MT-ND3 gene and DNA test is very important for the diagnosis of the disease.

Acute Auditory Agnosia Resulted from MELAS Syndrome / 听力学及言语疾病杂志

Objective To investigate the clinical features,etiology,diagnosis and treatment of acute auditory agnosia.Methods We studied the clinical manifestation,diagnosis and treatment of acute auditory agnosia in a patient in our hospital.Results A 28 year oldyoung woman visited our department because she suffered from the tinnitus for 7 days and she could not distinguish the semantics for 1 day.There were no other abnormal symptoms in the central and peripheral nervous system on admission.Audiological testing showed normal,language testing showed that the speech discrimination score was zero.MRI showed extensive damage to temporal lope.MR spectroscopy revealed increased lactate and reduced N-acetyl aspartate.Acute auditory agnosia resulted from mitochondrial myopathy was considered.After symptomatic treatment,the symptoms were significantly improved.Molecular genetics examination showed the A3243G mtDNA mutation,further confirmed the diagnosis of mitochondrial encephalomyopathy with lactic acidosis and stroke like episodes (MELAS) syndrome.Conclusion Acute auditory agnosia and acute tinnitus can be the first symptoms in MELAS,thus,MELAS should be suspected in patients with acute auditory agnosia,acute tinnitus,sudden hearing loss in children and youth.Imaging examination plays an important role in the etiological diagnosis of acute auditory agnosia.

Late-onset MELAS with Chronic Kidney Disease

Mitochondrial encephalomyopathy with lactic acid and stroke-like episodes (MELAS) is a multisystem mitochondrial disorder that typically presents in childhood. We report a case of MELAS syndrome diagnosed in a 45-year-old man presented with chronic kidney disease before a stroke-like episode. Genetic testing revealed a m.3243A>G point mutation in the mtDNA. The original diagnostic criteria for MELAS required the onset of stroke-like episodes prior to 40 years of age but this case demonstrates that disease onset may delay in certain individuals.

Acute Intestinal Pseudo-Obstruction in a Patient with MELAS Syndrome

No abstract available.

Síndrome de Melas: correlación clínica con hallazgos imagenológicos en espectroscopia y tractografía, reporte de caso / Melas syndrome: clinical correlation with imaging findings in spectroscopy and tractography, case report

El síndrome de Melas es una enfermedad de herencia mitocondrial caracterizada por encefalopatía mitocondrial, acidosis láctica y eventos similares a ataque cerebrovascular, secundaria a una mutación en los genes que codifican las proteínas transportadoras de electrones, limitando la producción energética y generando disfunción multiorgánica, que afecta principalmente el sistema músculo esquelético y el sistema nervioso, lo que está en correlación con las características clínicas que presentan los pacientes. El diagnostico se basa en la sospecha clínica, los hallazgos paraclínicos e imagenológicos y la confirmación de la mutación a través del estudio genético. No existe tratamiento específico, se basa únicamente en el manejo sintomático y requiere apoyo multidisciplinario. Presentamos el caso de un paciente con antecedente de Melas, que ingresó por evento cerebrovascular isquémico bioccipital y correlación con hallazgos en neuroimágenes (espectroscopia y tractografía).

Melas syndrome is a disease characterized by mitochondrial inheritance of mitochondrial encephalopathy, lactic acidosis and events like stroke secondary to a mutation in the gene encoding the electron transport proteins limiting energy production and generating multiorgan dysfunction being affected mainly musculoskeletal system and the nervous system which correlates with the clinical characteristics presented by patients. The diagnosis is based on clinical suspicion, laboratory, and imaging findings and confirmation of the mutation through genetic study. No specific treatment is Is available, but symptomatic treatment is needed and requires multidisciplinary support. We report a patient with a history of Melas who who had bioccipital cerebral ischemic event and correlation with findings in neuroimaging (spectroscopy and tractography).

SÍNDROME DE MELAS COMO CAUSA INHABITUAL DE ACV ISQUÉMICO: Presentación de un caso clínico / MELAS SYNDROME as unusual ischemic stroke CAUSE: Presentation of a clinical case

Las mitocondriopatías son un amplio espectro de patologías caracterizadas por un metabolismo mitocondrial anómalo. Dentro de estas enfermedades se incluye la MELAS, cuya sigla en inglés significa encefalomiopatía mitocondrial, acidosis láctica y episodios “stroke-like”. Se trata de un síndrome de presentación clínica heterogénea que debe considerarse como causa inhabitual de accidente cerebro vascular-símil en los pacientes jóvenes. La resonancia magnética puede otorgar la clave diagnóstica al mostrar áreas de isquemia cerebral sin respeto de los territorios vasculares arteriales. La biopsia muscular con el hallazgo de las fibras rojas rasgadas puede sugerir enfermedad mitocondrial. El diagnóstico definitivo de MELAS se realiza mediante análisis genético por demostración de mutaciones en el ADNm. Se presenta el primer caso clínico confirmado de MELAS con episodios “stroke-like” en la edad adulta reportado en nuestro país

Mitochondriopathies are a wide spectrum of diseases characterized by abnormal mitochondrial metabolism. Within these diseases is the MELAS, whose acronym means mitochondrial encephalomyopathy, lactic acidosis and "stroke-like" episodes. It is a syndrome of heterogeneous clinical presentation that should be considered as an unusual cause of stroke in young patients. Brain MRI can provide the diagnostic key with areas of ischemia without respect for arterial vascular territories. Muscle biopsy may suggest mitochondrial disease with the finding of ragged red fibers. The definitive diagnosis of MELAS is done through genetic analysis with mutations in the mtDNA. We described the first clinical confirmed case of MELAS with "stroke-like" episodes in adulthood reported in our country.

Case studies of two families with MIDD and MELAS: heteroplasmy level in m. 3243A>G mutation and the first report on m.3271T>C mutation in Colombia / Dos familias con midd y melas: nivel de heteroplasmia de la mutación m. 3243a>g y primer reporte de la mutación m.3271t>c en colombia

MELAS syndrome (mitochondrial encephalomyopathy, lactic acidosis, and stroke-like episodes) and MIDD syndrome (maternally inherited diabetes and deafness) are mitochondrial diseases caused in most cases by the same mutation m.3243A> G, which affects the gene MT-TL1. The cases of two families with MELAS are presented here. In the first case, the m.3243A>G mutation was detected and the heteroplasmy level in blood, urine and oral mucosa were determined, finding a great phenotypic variability: the patient had higher heteroplasmy in the three tissues compared against oligosymptomatic relatives, and the mother had high blood sugar levels and hearing loss, suggesting a phenotype near to MIDD. In the second family, the m.3271T>C mutation was detected, which constitutes the first case reported in Colombia. These findings suggest that MIDD and MELAS, often described as distinct entities, are part of the same entity with variable expressivity partially depending on heteroplasmy.

El síndrome MELAS (encefalomiopatía mitocondrial, acidosis láctica y episodios similares a isquemia cerebral) y el síndrome MIDD (diabetes y sordera de herencia materna) son enfermedades mitocondriales producidas en la mayor parte de los casos por una misma mutación: la m.3243A>G que afecta al gen MT-TL1. Se presentan los casos de dos familias con MELAS. En la primera se detecta la mutación m.3243A>G y se determina el nivel de heteroplasmia en sangre, orina y mucosa oral, con lo que se evidencia una gran variabilidad fenotípica: la paciente tenía una mayor heteroplasmia en los tres tejidos en comparación con sus familiares oligosintomáticos y la madre tenía una glicemia elevada e hipoacusia, sugiriendo un fenotipo cercano al MIDD. En la segunda familia se detecta la mutación m.3271T>C, siendo el primer caso reportado en Colombia. Estos hallazgos sugieren que el MIDD y el MELAS, descritos frecuentemente como entidades distintas, hacen parte de una misma entidad con expresividad variable dependiendo en parte de la heteroplasmia.