Mechanisms of unexpected death and autopsy findings in Leigh syndrome (subacute necrotising encephalomyelopathy)

Genotype-phenotype correlation in IARS2-related diseases: A case report and review of literature

Isoleucyl-tRNA synthetase 2 (IARS2) encodes mitochondrial isoleucine-tRNA synthetase. Pathogenic variants in the IARS2 gene are associated with mitochondrial disease. We report a female with IARS2 compound heterozygous variants, p.Val499Glyfs*14 and p.Arg784Trp who presented with infantile spasms, Leigh disease and Wolff-Parkinson White (WPW) pattern. This report expands the phenotypic spectrum of IARS2-related disease.

Two Cases of Leigh Syndrome in One Family: Diagnostic Challenges and Clinical Management Experience in Latvia

Leigh syndrome is a neurodegenerative disorder with an incidence of 1 : 40,000 live births. The clinical presentation of LS is highly variable with heterogeneity in the disease-associated symptoms of cerebellar, motor, and extrapyramidal dysfunction and common infections. There is no effective treatment for this condition; as such, the prognosis of this condition is very poor with death occurring within the first few years of life. In this study, we report the first LS case in Latvia with SURF1 pathogenic variants in two siblings. The difficulties encountered establishing a diagnosis for the first proband and the effective prenatal diagnosis for the second offspring that led to termination of the pregnancy are discussed.

Leigh syndrome in an infant: autopsy and histopathology findings

Leigh syndrome is an inherited neurodegenerative disorder of infancy that typically manifests between 3 and 12 months of age. The common neurological manifestations are developmental delay or regression, progressive cognitive decline, dystonia, ataxia, brainstem dysfunction, epileptic seizures, and respiratory dysfunction. Although the disorder is clinically and genetically heterogeneous, the histopathological and radiological features characteristically show focal and bilaterally symmetrical, necrotic lesions in the basal ganglia and brainstem. The syndrome has a characteristic histopathological signature that helps in clinching the diagnosis. We discuss these unique findings on autopsy and radiology in a young infant who succumbed to a subacute, progressive neurological illness suggestive of Leigh syndrome. Our case highlights that Leigh syndrome should be considered in the differential diagnosis of infantile-onset, subacute neuroregression with dystonia and seizures, a high anion gap metabolic acidosis, normal ketones, elevated lactates in blood, brain, and urine, and bilateral basal ganglia involvement.

Genetic diseases mimicking multiple sclerosis

Multiple sclerosis (MS) is an inflammatory neurodegenerative disorder manifesting as gradual or progressive loss of neurological functions. Most patients present with relapsing-remitting disease courses. Extensive research over recent decades has expounded our insights into the presentations and diagnostic features of MS. Groups of genetic diseases, CADASIL and leukodystrophies, for example, have been frequently misdiagnosed with MS due to some overlapping clinical and radiological features. The delayed identification of these diseases in late adulthood can lead to severe neurological complications. Herein we discuss genetic diseases that have the potential to mimic multiple sclerosis, with highlights on clinical identification and practicing pearls that may aid physicians in recognizing MS-mimics with genetic background in clinical settings.

A case report on a novel MT-ATP6 gene variation in atypical mitochondrial Leigh syndrome associated with bilateral basal ganglia calcifications

Leigh Syndrome (LS) is a rare, hereditary progressive neurodegenerative disorder of infancy or early childhood associated with a highly variable clinical presentation even among siblings. Further, genetic heterogeneity makes its diagnosis complicated. Its causative genetic variations are notified in some of the mitochondrial and nuclear genes. Here, we report an atypical case of LS in a 9-year-old boy associated with a novel variation in MT-ATP6 gene. The atypical findings were Bilateral Basal Ganglia Calcification (BGC) and late survival age in the patient. Analyses of the Whole Mitochondrial Genome Sequencing (WMGS) results of the recruited patient and his mother at different read coverage, first at 100× and later repeated at 500×, revealed a novel disease-associated variation in the already known disease-associated MT-ATP6 gene. In conclusion, the present study indicates amalgamation of both neuro-imaging and Next Generation Sequencing (NGS) Technologies aiding the proper diagnosis of LS in atypical cases.

The neuroimaging of Leigh syndrome: case series and review of the literature

Leigh syndrome by definition is (1) a neurodegenerative disease with variable symptoms, (2) caused by mitochondrial dysfunction from a hereditary genetic defect and (3) accompanied by bilateral central nervous system lesions. A genetic etiology is confirmed in approximately 50% of patients, with more than 60 identified mutations in the nuclear and mitochondrial genomes. Here we review the clinical features and imaging studies of Leigh syndrome and describe the neuroimaging findings in a cohort of 17 children with genetically confirmed Leigh syndrome. MR findings include lesions in the brainstem in 9 children (53%), basal ganglia in 13 (76%), thalami in 4 (24%) and dentate nuclei in 2 (12%), and global atrophy in 2 (12%). The brainstem lesions were most frequent in the midbrain and medulla oblongata. With follow-up an increased number of lesions from baseline was observed in 7 of 13 children, evolution of the initial lesion was seen in 6, and complete regression of the lesions was seen in 3. No cerebral white matter lesions were found in any of the 17 children. In concordance with the literature, we found that Leigh syndrome follows a similar pattern of bilateral, symmetrical basal ganglia or brainstem changes. Lesions in Leigh syndrome evolve over time and a lack of visible lesions does not exclude the diagnosis. Reversibility of lesions is seen in some patients, making the continued search for treatment and prevention a priority for clinicians and researchers.

Leigh syndrome: Resolving the clinical and genetic heterogeneity paves the way for treatment options

Leigh syndrome is a progressive neurodegenerative disorder, affecting 1 in 40,000 live births. Most patients present with symptoms between the ages of three and twelve months, but adult onset Leigh syndrome has also been described. The disease course is characterized by a rapid deterioration of cognitive and motor functions, in most cases resulting in death due to respiratory failure. Despite the high genetic heterogeneity of Leigh syndrome, patients present with identical, symmetrical lesions in the basal ganglia or brainstem on MRI, while additional clinical manifestations and age of onset varies from case to case. To date, mutations in over 60 genes, both nuclear and mitochondrial DNA encoded, have been shown to cause Leigh syndrome, still explaining only half of all cases. In most patients, these mutations directly or indirectly affect the activity of the mitochondrial respiratory chain or pyruvate dehydrogenase complex. Exome sequencing has accelerated the discovery of new genes and pathways involved in Leigh syndrome, providing novel insights into the pathophysiological mechanisms. This is particularly important as no general curative treatment is available for this devastating disorder, although several recent studies imply that early treatment might be beneficial for some patients depending on the gene or process affected. Timely, gene-based personalized treatment may become an important strategy in rare, genetically heterogeneous disorders like Leigh syndrome, stressing the importance of early genetic diagnosis and identification of new genes/pathways. In this review, we provide a comprehensive overview of the most important clinical manifestations and genes/pathways involved in Leigh syndrome, and discuss the current state of therapeutic interventions in patients.

A guide to diagnosis and treatment of Leigh syndrome

Leigh syndrome is a devastating neurodegenerative disease, typically manifesting in infancy or early childhood. However, also late-onset cases have been reported. Since its first description by Denis Archibald Leigh in 1951, it has evolved from a postmortem diagnosis, strictly defined by histopathological observations, to a clinical entity with indicative laboratory and radiological findings. Hallmarks of the disease are symmetrical lesions in the basal ganglia or brain stem on MRI, and a clinical course with rapid deterioration of cognitive and motor functions. Examinations of fresh muscle tissue or cultured fibroblasts are important tools to establish a biochemical and genetic diagnosis. Numerous causative mutations in mitochondrial and nuclear genes, encoding components of the oxidative phosphorylation system have been described in the past years. Moreover, dysfunctions in pyruvate dehydrogenase complex or coenzyme Q10 metabolism may be associated with Leigh syndrome. To date, there is no cure for affected patients, and treatment options are mostly unsatisfactory. Here, we review the most important clinical aspects of Leigh syndrome, and discuss diagnostic steps as well as treatment options.

Mitochondrial disease in childhood: nuclear encoded

Primary mitochondrial disorders are clinically and genetically heterogeneous, caused by an alteration(s) in either mitochondrial DNA or nuclear DNA, and affect the respiratory chain's ability to undergo oxidative phosphorylation, leading to decreased production of adenosine triphosphophate and subsequent energy failure. These disorders may present at any age, but children tend to have an acute onset of disease compared with subacute or slowly progressive presentation in adults. Varying organ involvement also contributes to the phenotypic spectrum seen in these disorders. The childhood presentation of primary mitochondrial disease is mainly due to nuclear DNA mutations, with mitochondrial DNA mutations being less frequent in childhood and more prominent in adulthood disease. The clinician should be aware of the pediatric presentation of mitochondrial disease and have an understanding of the myriad of nuclear genes responsible for these disorders. The nuclear genes can be best understood by utilizing a classification system of location and function within the mitochondria.

Sudden death in Leigh syndrome: an autopsy case

The present report describes the sudden death of a 3-year-old female child who had been clinically diagnosed with Leigh syndrome.Leigh syndrome is a heterogeneous progressive neurodegenerative disorder, which is characterized by focal or bilateral lesions in the thalamus, basal ganglia, brainstem, cerebellum, and spinal cord. Affected patients exhibit a variable clinical picture that frequently includes psychomotor retardation or regression, recurrent episodes of vomiting, failure to thrive, and signs of brainstem and basal ganglia dysfunction.The child was found dead in bed. Autopsy described the presence of symmetrical, necrotizing lesions scattered within the basal ganglia, thalamus, diencephalon, brainstem, and spinal-cord gray matter and revealed the presence of gastric contents in the upper and lower airways. We report the results of genetic investigations and describe the histological and immunohistochemical features that confirmed the diagnosis. These findings suggest that Leigh syndrome should be regarded as predisposing children to sudden death, especially by asphyxia secondary to the neurological disorder.

Medical treatment with thiamine, coenzyme Q, vitamins E and C, and carnitine improved obstructive sleep apnea in an adult case of Leigh disease

PURPOSE

The multi-organ involvement of mitochondrial diseases means that patients are likely to be more vulnerable to sleep disturbances. We aimed to assess if early recognition and treatment of obstructive sleep apnea (OSA) in patients with Leigh disease may influence primary disease outcome.

METHODS

We describe a case of adult-onset Leigh disease presenting as severe brainstem encephalopathy of subacute onset. Based on the clinical symptoms that developed after the appearance of the neurological disease, an attended overnight polysomnography examination was performed.

RESULTS

A marked clinical recovery was seen after administration of high doses of thiamine, coenzyme Q, L-carnitine, and vitamins C and E, combined with effective treatment with continuous positive airway pressure for the underlying severe obstructive sleep apnea (OSA). The latter condition was diagnosed on the basis of suggestive symptoms that appeared a few weeks before the establishment of the neurological disease. The improvement in the neurological disease (based on clinical and brain MRI features) with the appropriate medical treatment also resulted in a significant improvement in the OSA.

CONCLUSIONS

Early recognition and treatment of sleep apnea may not only improve sleep and overall quality of life but also ameliorate the deleterious effects of nocturnal desaturations on the neurological features. This may be crucial for disease outcome when added to the generally advised pharmacological therapy.

Ammonium accumulation and cell death in a rat 3D brain cell model of glutaric aciduria type I

Glutaric aciduria type I (glutaryl-CoA dehydrogenase deficiency) is an inborn error of metabolism that usually manifests in infancy by an acute encephalopathic crisis and often results in permanent motor handicap. Biochemical hallmarks of this disease are elevated levels of glutarate and 3-hydroxyglutarate in blood and urine. The neuropathology of this disease is still poorly understood, as low lysine diet and carnitine supplementation do not always prevent brain damage, even in early-treated patients. We used a 3D in vitro model of rat organotypic brain cell cultures in aggregates to mimic glutaric aciduria type I by repeated administration of 1 mM glutarate or 3-hydroxyglutarate at two time points representing different developmental stages. Both metabolites were deleterious for the developing brain cells, with 3-hydroxyglutarate being the most toxic metabolite in our model. Astrocytes were the cells most strongly affected by metabolite exposure. In culture medium, we observed an up to 11-fold increase of ammonium in the culture medium with a concomitant decrease of glutamine. We further observed an increase in lactate and a concomitant decrease in glucose. Exposure to 3-hydroxyglutarate led to a significantly increased cell death rate. Thus, we propose a three step model for brain damage in glutaric aciduria type I: (i) 3-OHGA causes the death of astrocytes, (ii) deficiency of the astrocytic enzyme glutamine synthetase leads to intracerebral ammonium accumulation, and (iii) high ammonium triggers secondary death of other brain cells. These unexpected findings need to be further investigated and verified in vivo. They suggest that intracerebral ammonium accumulation might be an important target for the development of more effective treatment strategies to prevent brain damage in patients with glutaric aciduria type I.

Update on nuclear mitochondrial genes and neurologic disorders

The majority of primary mitochondrial disorders are due to nuclear gene mutations, not aberrations within the mitochondrial genome. The nervous system is frequently involved due to its high-energy demands. Many nonspecific neurologic symptoms may be present in mitochondrial disease; however, there are well-recognized red flags that should alert the clinician to the possibility of mitochondrial disease. There is an ever increasing number of nuclear gene mutations discovered that play a role in primary mitochondrial disease and its neurologic symptomatology. Neurologists need to be aware of the wide neurologic presentation, the red-flag symptoms, and the nuclear gene mutations involved in the pathophysiology of mitochondrial disease to diagnose and manage this patient population.

Late-adult onset Leigh syndrome

We report an illustrative case of a 74-year-old man who, in the absence of intercurrent illness, presented with rapid cognitive decline. MRI showed bilateral, symmetrical, high T2-weighted signal in the anterior basal ganglia and medial thalami, extending to the periaqueductal grey matter, basal ganglia and basal frontal lobes. A (18)F-fluorodeoxyglucose-positron emission tomography scan showed widespread reduction of metabolism in the cortex of the frontal, temporal and parietal lobes, posterior cingulate gyrus, precuneus and caudate nuclei, with sparing of the sensorimotor cortex, thalami and lentiform nuclei. A mild vitamin B12 deficiency was found and despite normal thiamine levels, intravenous (IV) thiamine and vitamin B therapy was commenced, with a short course of IV methylprednisolone and tetracycline. Repeat neuropsychological assessment four weeks following treatment revealed increased alertness and interactiveness but significant cognitive decline persisted. Unexpectedly, the patient suffered a transmural anterior myocardial infarction six weeks after presentation and died within 24hours. An a autopsy showed: global reduction in cytochrome oxidase (COX) activity in all skeletal muscles examined; bilateral, symmetrical, hypervascular, focally necrotizing lesions in the substantia nigra, periaqueductal grey matter, superior colliculi, medial thalami anteriorly and posteriorly, as well as in the putamena but the mammillary bodies were not affected. Biochemical analysis of fresh muscle confirmed selective deficiency of complex IV of the oxidative phosphorylation chain. A diagnosis of late-adult onset Leigh syndrome was made. Multiple genetic studies failed to identify the specific underlying mutation. The relevant literature is reviewed.

Complex I deficiency due to loss of Ndufs4 in the brain results in progressive encephalopathy resembling Leigh syndrome

To explore the lethal, ataxic phenotype of complex I deficiency in Ndufs4 knockout (KO) mice, we inactivated Ndufs4 selectively in neurons and glia (NesKO mice). NesKO mice manifested the same symptoms as KO mice including retarded growth, loss of motor ability, breathing abnormalities, and death by approximately 7 wk. Progressive neuronal deterioration and gliosis in specific brain areas corresponded to behavioral changes as the disease advanced, with early involvement of the olfactory bulb, cerebellum, and vestibular nuclei. Neurons, particularly in these brain regions, had aberrant mitochondrial morphology. Activation of caspase 8, but not caspase 9, in affected brain regions implicate the initiation of the extrinsic apoptotic pathway. Limited caspase 3 activation and the predominance of ultrastructural features of necrotic cell death suggest a switch from apoptosis to necrosis in affected neurons. These data suggest that dysfunctional complex I in specific brain regions results in progressive glial activation that promotes neuronal death that ultimately results in mortality.

Sudden adult death

In the investigation of sudden death in adults, channelopathies, such as long QT syndrome, have risen to the fore in the minds of forensic pathologists in recent years. Examples of these disorders are touched upon in this review as an absence of abnormal findings at postmortem examination is characteristic and the importance of considering the diagnosis lies in the heritable nature of these conditions. Typically, a diagnosis of a possible channelopathy is evoked as an explanation for a 'negative autopsy' in a case of apparent sudden natural death. However, the one potential adverse effect of this approach is that subtle causes of sudden death may be overlooked. The intention of this article is to review and discuss potential causes of sudden adult death (mostly natural) that should be considered before resorting to a diagnosis of possible channelopathy. Nonetheless, it becomes apparent that many of the potential causes of sudden death can have a genetic basis. Thus, it becomes an important consideration that there may be a genetic basis to sudden death that extends beyond the negative autopsy.

Leigh and Leigh-like syndrome in children and adults

Leigh syndrome (also termed subacute, necrotizing encephalopathy) is a devastating neurodegenerative disorder, characterized by almost identical brain changes, e.g., focal, bilaterally symmetric lesions, particularly in the basal ganglia, thalamus, and brainstem, but with considerable clinical and genetic heterogeneity. Clinically, Leigh syndrome is characterized by a wide variety of abnormalities, from severe neurologic problems to a near absence of abnormalities. Most frequently the central nervous system is affected, with psychomotor retardation, seizures, nystagmus, ophthalmoparesis, optic atrophy, ataxia, dystonia, or respiratory failure. Some patients also present with peripheral nervous system involvement, including polyneuropathy or myopathy, or non-neurologic abnormalities, e.g., diabetes, short stature, hypertrichosis, cardiomyopathy, anemia, renal failure, vomiting, or diarrhea (Leigh-like syndrome). In the majority of cases, onset is in early childhood, but in a small number of cases, adults are affected. In the majority of cases, dysfunction of the respiratory chain (particularly complexes I, II, IV, or V), of coenzyme Q, or of the pyruvate dehydrogenase complex are responsible for the disease. Associated mutations affect genes of the mitochondrial or nuclear genome. Leigh syndrome and Leigh-like syndrome are the mitochondrial disorders with the largest genetic heterogeneity.