Clinical profile and outcome of cardiac involvement in MELAS syndrome

A Case Report of a Clinically Suspected Diagnosis of Mitochondrial Encephalomyopathy, Lactic Acidosis, and Stroke-Like Episodes (MELAS) Syndrome With Cardiac Impairment

This case report presents a description of a hypertrophic left ventricle with reduced ejection fraction in a man in his mid-twenties with clinical, radiologic, and biochemical features of a rare syndrome called mitochondrial encephalomyopathy, lactic acidosis, and stroke-like episodes (MELAS). A literature review of this uncommon syndrome and MELAS cardiomyopathy has been conducted.

Late-onset MELAS syndrome in a 46-year-old man with initial symptom of chest tightness: a case report

Background

Mitochondrial Encephalomyopathy, Lactic Acidosis, and Stroke-like episodes (MELAS) syndrome is a rare mitochondrial disorder caused by mutations in mitochondrial DNA, resulting in impaired energy production and affecting multiple organs. We present a suspected MELAS syndrome case with the initial symptom of chest tightness.

Case summary

A 46-year-old man sought medical attention due to progressively worsening chest tightness during physical activity. He had been receiving treatment for type 2 diabetes for 15 years. One year ago, he presented with symptoms of hearing impairment. Transthoracic echocardiography revealed increased thickness of the left ventricular wall. Serum protein electrophoresis showed no evidence of light-chain amyloidosis, and the 99mTc-3,3-diphosphono-1,2-propanodicarboxylic acid scan showed no definite uptake in the heart muscle. The patient's head magnetic resonance imaging (MRI) indicated lacunar infarcts. The lactate threshold test was positive. The biopsy of the skeletal muscle showed broken red fibre infiltration on modified Gomori trichrome staining, and electron microscopy revealed signs of mitochondrial cardiomyopathy, including mild mitochondrial swelling, lipid accumulation, and myofibril damage. A whole-exome genetic test was used to detect the m.3243A>G mutation in the MT-TL1 gene. Based on these findings, MELAS syndrome was the most probable diagnosis.

Discussion

The patient presented with chest tightness in adulthood, without any accompanying psychoneurological symptoms. However, the patient presented with other symptoms, including diabetes mellitus, hearing loss, abnormal lactate levels, ischaemic lesions on head MRI, and left ventricular hypertrophy. By identifying a mutation in the MT-TL1 gene and conducting a muscle biopsy, the diagnosis of MELAS syndrome was definitively confirmed.

Hypertrophic cardiomyopathy as the initial presentation of mitochondrial disease in an infant born to a diabetic mother

In contrast to hypertrophic cardiomyopathy caused by maternal diabetes, neonatal mitochondrial cardiomyopathy is rare and has a poor prognosis. We report an infant born to a mother with maternal diabetes with persistent ventricular hypertrophy, who was diagnosed with mitochondrial disease associated with m.3243A>G mutation in a mitochondrial tRNA leucine 1 gene. The hypertrophic cardiomyopathy was his initial and only clinical presentation.

Sudden cardiac death in childhood hypertrophic cardiomyopathy

The most prevalent cause of mortality in children with hypertrophic cardiomyopathy (HCM) is sudden cardiac death (SCD), which happens more frequently than in adult patients. Risk stratification tactics have generally been drawn from adult practice, however emerging data has revealed significant disparities between children and adult cohorts, implying the need for pediatric-specific risk stratification methodologies. We conducted an all-language literature search on Medline, Cochrane, Embase, and Google Scholar until October 2021. The following search strings and Medical Subject Heading (MeSH) terms were used: "HCM," "SCD," "Sudden Cardiac Death," and "Childhood Onset HCM." We explored the literature on the risk of SCD in HCM for its epidemiology, pathophysiology, the role of various genes and their influence, associated complications leading to SCD and preventive and treatment modalities. Childhood-onset HCM is linked to significant life-long morbidity and mortality, including a higher SCD rate in children than in adults. The present focus is on symptom relief and avoiding illness-related consequences, but the prospect of future disease-modifying medicines offers an intriguing opportunity to alter disease expression and outcomes in these young individuals. Current preventive recommendations promote implantable cardioverter defibrillator placement based on cumulative risk factor thresholds, although they have been demonstrated to have weak discriminating capacity. This article addresses questions and discusses the etiology, risk factors, and method to risk stratification for SCD in children with HCM.

Subclinical cardiac involvement present as electrocardiographic abnormalities in various neuromuscular diseases

Background

Cardiac involvement is commonly present in various neuromuscular diseases which may develop life-threatening consequences. The early manifestation is often asymptomatic which however has been insufficiently studied.

Objectives

We aim to characterize electrocardiographic (ECG) changes in neuromuscular diseases without cardiac symptoms.

Methods

Adults having genetically and/or pathologically confirmed type 1 myotonic dystrophy (DM1), Becker muscular dystrophy (BMD), limb girdle muscular dystrophies (LGMDs) and mitochondrial diseases (MtDs) but without history of heart diseases and cardiovascular symptoms were enrolled. The 12-lead ECG characteristics and other test results at diagnosis were retrieved and analyzed.

Results

196 patients with neuromuscular diseases (44 DM1, 25 BMD, 82 LGMDs, 45 MtDs) were consecutively enrolled. ECG abnormalities were identified in 107 (54.6%) patients with a prevalence of 59.1% in DM1, 76.0% in BMD, 40.2% in LGMDs and 64.4% in MtDs. Conduction block was more commonly present in DM1 than the other groups (P < 0.01), which had a longest PR interval and QRS duration of 186.1 ± 38.3 ms and 104.2 [90.0-108.0]ms, respectively. QT prolongation was most frequently seen in DM1 (P < 0.001). Left ventricular hypertrophy features were found in BMD, LGMDs and MtDs (P < 0.05) without intergroup difference, while a significantly higher right ventricular amplitude is observed in BMD than in other groups (P < 0.001).

Conclusions

Subclinical cardiac involvement is commonly present as ECG abnormalities in multiple adult neuromuscular diseases before associated symptoms occur and show diversity in different groups.

Cardiac Involvement in Mitochondrial Disorders

PURPOSE OF REVIEW

We review pathophysiology and clinical features of mitochondrial disorders manifesting with cardiomyopathy.

RECENT FINDINGS

Mechanistic studies have shed light into the underpinnings of mitochondrial disorders, providing novel insights into mitochondrial physiology and identifying new therapeutic targets. Mitochondrial disorders are a group of rare genetic diseases that are caused by mutations in mitochondrial DNA (mtDNA) or in nuclear genes that are essential to mitochondrial function. The clinical picture is extremely heterogeneous, the onset can occur at any age, and virtually, any organ or tissue can be involved. Since the heart relies primarily on mitochondrial oxidative metabolism to fuel contraction and relaxation, cardiac involvement is common in mitochondrial disorders and often represents a major determinant of their prognosis.

Adult-onset MELAS syndrome in a 51-year-old woman without typical clinical manifestations: a case report

Background

Mitochondrial encephalomyopathy with lactic acidosis and stroke-like episodes (MELAS) syndrome is a multi-organ disorder resulting from mitochondrial DNA (mtDNA) mutations. We report a case of suspected MELAS syndrome that progressed to left ventricular dysfunction 24 years after an initial diagnosis of atrioventricular block (AVB).

Case summary

A 51-year-old woman was referred to heart failure clinic because of dyspnoea on exertion and progressive cardiomegaly. She had a dual-chamber pacemaker implanted for 24 years because of a high-degree AVB. She was treated for diabetes mellitus for 23 years and used hearing aids for 12 years because of sensorineural hearing loss. Transthoracic echocardiography revealed reduced left ventricular ejection fraction (26%), with increased thickness and unusual texture of the myocardium. The absence of abnormal findings on serum and urine protein electrophoresis suggested that light-chain amyloidosis was unlikely. In addition, ^99mTc-3,3-diphosphono-1,2-propanodicarboxylic acid scintigraphy revealed no definite uptake in the myocardium. Endomyocardial biopsy revealed a hypertrophy of myocytes in haematoxylin-eosin staining, and electron microscopy revealed a disarrangement of mitochondrial cristae, which were suggestive of mitochondrial cardiomyopathy. A mtDNA test detected the m.3243A > G mutation in the MT-TL1 gene. According to these findings, MELAS syndrome was the most probable diagnosis despite the absence of common symptoms such as stroke-like episodes or lactic acidosis.

Discussion

The patient had progressed to heart failure with reduced ejection fraction 24 years after the first cardiac manifestation. An identification of the mutation in the MT-TL1 gene, indicative of MELAS syndrome, enabled the diagnosis of MELAS syndrome without typical manifestations.

Arginine for the Treatment of Mitochondrial Encephalopathy, Lactic Acidosis, and Stroke-Like Episodes: A Systematic Review

Mitochondrial encephalopathy, lactic acidosis, and stroke-like episodes (MELAS) syndrome is a mitochondrial disease that lacks a definitive treatment. Lately, there has been an increased interest in the scientific community about the role of arginine in the short and long-term settings of the disease. We aim to conduct a systematic review of the clinical use of arginine in the management of MELAS and explore the role of arginine in the pathophysiology of the disease. We used PubMed advanced-strategy searches and only included full-text clinical trials on humans written in the English language. After applying the inclusion/exclusion criteria, four clinical trials were reviewed. We used the Meta-analysis of Observational Studies in Epidemiology (MOOSE) guidelines and Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) protocol for this systematic review. We used the Cochrane Collaboration risk-of-bias tool to assess the bias encountered in each study. Overall, IV arginine seems to be effective in improving symptoms during acute attacks of MELAS, while oral arginine supplementation increases endothelial function, preventing further stroke-like episodes.

Beyond Sarcomeric Hypertrophic Cardiomyopathy: How to Diagnose and Manage Phenocopies

PURPOSE OF REVIEW

We describe the most common phenocopies of hypertrophic cardiomyopathy, their pathogenesis, and clinical presentation highlighting similarities and differences. We also suggest a step-by-step diagnostic work-up that can guide in differential diagnosis and management.

RECENT FINDINGS

In the last years, a wider application of genetic testing and the advances in cardiac imaging have significantly changed the diagnostic approach to HCM phenocopies. Different prognosis and management, with an increasing availability of disease-specific therapies, make differential diagnosis mandatory. The HCM phenotype can be the cardiac manifestation of different inherited and acquired disorders presenting different etiology, prognosis, and treatment. Differential diagnosis requires a cardiomyopathic mindset allowing to recognize red flags throughout the diagnostic work-up starting from clinical and family history and ending with advanced imaging and genetic testing. Different prognosis and management, with an increasing availability of disease-specific therapies make differential diagnosis mandatory.

Delay in diagnosing a patient with mitochondrial encephalomyopathy, lactic acidosis, and stroke-like episodes (MELAS) syndrome who presented with status epilepticus and lactic acidosis: a case report

Background

Mitochondrial encephalomyopathy, lactic acidosis, and stroke-like episode syndrome is a rare mitochondrial genetic disorder that can present with a variety of clinical manifestations, including stroke, hearing loss, seizures, and lactic acidosis. The most common genetic mutation associated with this syndrome is M.3243A>G. The main underlying mechanism of the disease relates to protein synthesis, energy depletion, and nitric oxide deficiency. Controlling disease complications and improving patient quality of life are the primary aims of treatment options.

Case presentation

A 28-year-old Arabic female visited Al-Amiri Hospital in Kuwait. The patient was newly diagnosed with mitochondrial encephalomyopathy, lactic acidosis, and stroke-like episode syndrome following her admission as a case of status epilepticus requiring further investigation. The patient’s seizures were controlled, and she was evaluated to rule out the most serious complications by carrying out appropriate clinical, laboratory, and radiological imaging. The patient was discharged from the hospital after 2 weeks with a follow-up plan.

Conclusion

This case report emphasizes the importance of considering mitochondrial encephalomyopathy, lactic acidosis, and stroke-like episode syndrome as a potential cause of status epilepticus with lactic acidosis in a young female patient with a past history of stroke-like episodes. It also stresses the most important workup to rule out every possible life-threatening complication to improve patients’ lives.

Diagnosis of adult‑onset MELAS with suspected recurrent strokes: A case report

Mitochondrial encephalomyopathy, lactic acidosis and stroke-like episodes (MELAS) is caused by mutations in mitochondrial DNA and is one of the most common syndromes among the mitochondrial diseases. Clinical manifestations typically occur before the age of 40 years. The present study reports a case of MELAS with a mutation in the adenine to guanine conversion at mitochondrial genome 3243 in a 48-year-old woman who was suspected of suffering from recurrent strokes. Finally, the genomic analysis confirmed the diagnosis of MELAS. This case highlights the importance of considering MELAS as a potential cause of recurrent stroke-like events if imaging findings are atypical for cerebral infarction, even among middle-aged patients with vascular risk factors.

Genetics of Cardiomyopathy: Clinical and Mechanistic Implications for Heart Failure

Genetic cardiomyopathies are an important cause of sudden cardiac death across all age groups. Genetic testing in heart failure clinics is useful for family screening and providing individual prognostic insight. Obtaining a family history of at least three generations, including the creation of a pedigree, is recommended for all patients with primary cardiomyopathy. Additionally, when appropriate, consultation with a genetic counsellor can aid in the success of a genetic evaluation. Clinical screening should be performed on all first-degree relatives of patients with genetic cardiomyopathy.

Genetics has played an important role in the understanding of different cardiomyopathies, and the field of heart failure (HF) genetics is progressing rapidly. Much research has also focused on distinguishing markers of risk in patients with cardiomyopathy using genetic testing. While these efforts currently remain incomplete, new genomic technologies and analytical strategies provide promising opportunities to further explore the genetic architecture of cardiomyopathies, afford insight into the early manifestations of cardiomyopathy, and help define the molecular pathophysiological basis for cardiac remodeling. Cardiovascular physicians should be fully aware of the utility and potential pitfalls of incorporating genetic test results into pre-emptive treatment strategies for patients in the preliminary stages of HF. Future work will need to be directed towards elucidating the biological mechanisms of both rare and common gene variants and environmental determinants of plasticity in the genotype-phenotype relationship. This future research should aim to further our ability to identify, diagnose, and treat disorders that cause HF and sudden cardiac death in young patients, as well as prioritize improving our ability to stratify the risk for these patients prior to the onset of the more severe consequences of their disease.

Unraveling an Unusual Phenocopy of Hypertrophic Cardiomyopathy: MELAS Syndrome

The mitochondrial myopathy, encephalopathy, lactic acidosis, and stroke-like episodes (MELAS) syndrome is an uncommon cause of cardiac hypertrophy, fibrosis, and dysfunction. It shares similar features to numerous other causes of left ventricular hypertrophy, and therefore, because of its rarity, may not be immediately considered as a diagnosis. Prompt recognition of clinical and cardiac imaging features may expedite diagnosis and management. We report the case of a 38-year-old man admitted with neurological symptoms and in whom the diagnostic workup led to the diagnosis of MELAS syndrome with cardiac involvement.

Hypertrophic Cardiomyopathy in Children: Pathophysiology, Diagnosis, and Treatment of Non-sarcomeric Causes

Hypertrophic cardiomyopathy (HCM) is a myocardial disease characterized by left ventricular hypertrophy not solely explained by abnormal loading conditions. Despite its rare prevalence in pediatric age, HCM carries a relevant risk of mortality and morbidity in both infants and children. Pediatric HCM is a large heterogeneous group of disorders. Other than mutations in sarcomeric genes, which represent the most important cause of HCM in adults, childhood HCM includes a high prevalence of non-sarcomeric causes, including inherited errors of metabolism (i.e., glycogen storage diseases, lysosomal storage diseases, and fatty acid oxidation disorders), malformation syndromes, neuromuscular diseases, and mitochondrial disease, which globally represent up to 35% of children with HCM. The age of presentation and the underlying etiology significantly impact the prognosis of children with HCM. Moreover, in recent years, different targeted approaches for non-sarcomeric etiologies of HCM have emerged. Therefore, the etiological diagnosis is a fundamental step in designing specific management and therapy in these subjects. The present review aims to provide an overview of the non-sarcomeric causes of HCM in children, focusing on the pathophysiology, clinical features, diagnosis, and treatment of these rare disorders.

Stable retention of chloramphenicol-resistant mtDNA to rescue metabolically impaired cells

The permanent transfer of specific mtDNA sequences into mammalian cells could generate improved models of mtDNA disease and support future cell-based therapies. Previous studies documented multiple biochemical changes in recipient cells shortly after mtDNA transfer, but the long-term retention and function of transferred mtDNA remains unknown. Here, we evaluate mtDNA retention in new host cells using ‘MitoPunch’, a device that transfers isolated mitochondria into mouse and human cells. We show that newly introduced mtDNA is stably retained in mtDNA-deficient (ρ0) recipient cells following uridine-free selection, although exogenous mtDNA is lost from metabolically impaired, mtDNA-intact (ρ+) cells. We then introduced a second selective pressure by transferring chloramphenicol-resistant mitochondria into chloramphenicol-sensitive, metabolically impaired ρ+ mouse cybrid cells. Following double selection, recipient cells with mismatched nuclear (nDNA) and mitochondrial (mtDNA) genomes retained transferred mtDNA, which replaced the endogenous mutant mtDNA and improved cell respiration. However, recipient cells with matched mtDNA-nDNA failed to retain transferred mtDNA and sustained impaired respiration. Our results suggest that exogenous mtDNA retention in metabolically impaired ρ+ recipients depends on the degree of recipient mtDNA-nDNA co-evolution. Uncovering factors that stabilize exogenous mtDNA integration will improve our understanding of in vivo mitochondrial transfer and the interplay between mitochondrial and nuclear genomes.

Genetic aspects of the oxidative phosphorylation dysfunction in dilated cardiomyopathy

Dilated cardiomyopathy is a frequent and extremely heterogeneous medical condition. Deficits in the oxidative phosphorylation system have been described in patients suffering from dilated cardiomyopathy. Hence, mutations in proteins related to this biochemical pathway could be etiological factors for some of these patients. Here, we review the clinical phenotypes of patients harboring pathological mutations in genes related to the oxidative phosphorylation system, either encoded in the mitochondrial or in the nuclear genome, presenting with dilated cardiomyopathy. In addition to the clinical heterogeneity of these patients, the large genetic heterogeneity has contributed to an improper allocation of pathogenicity for many candidate mutations. We suggest criteria to avoid incorrect assignment of pathogenicity to newly found mutations and discuss possible therapies targeting the oxidative phosphorylation function.

Impact of cardiovascular involvement on the clinical course of paediatric mitochondrial disorders

BACKGROUND

Primary mitochondrial disorders (PMD) are rare conditions resulting in progressive multi-organ failure. Cardiovascular involvement (CVI) has been reported in paediatric patients. However, its age-related prevalence, clinical presentation and prognostic impact are unresolved. We detailed CVI in a cohort of children diagnosed with PMD over two decades at a tertiary referral centre.

RESULTS

We enrolled 86 PMD patients (M/F = 30/56; mean age 6.4 ± 8.58 years). CVI was detected in 31 patients (36%), with mean age at onset of 5.7 ± 7.8 years including the pre- and neonatal phase in 14, often representing the first sign of PMD (42% of those with CVI). Heart disease resulted more common in males and in children with specific aetiologies (Barth, TMEM70 and MELAS syndromes). Hypertrophic, non-compaction and dilated cardiomyopathies were the prevalent disorders, although pulmonary arterial hypertension was also found. Adverse cardiac events (heart failure, resuscitated cardiac arrest, ICD/PM implantation, sudden death) occurred in 19% of children with CVI over a follow-up period of 5.4 ± 4.3 years. All-cause mortality was higher in patients with CVI compared to those without CVI (45.1% vs 21.8%; p < 0.01); female sex, age at onset < 5 years, acute heart failure at presentation and diabetes also proved independent predictors of outcome.

CONCLUSION

Cardiovascular involvement occurred in over one-third of children diagnosed with PMD, often at a very early age, and was associated with adverse prognosis. Final outcome of PMD-related CVI was influenced by the specific underlying aetiology, suggesting the need for tailored management of heart failure and sudden death prevention.