Successive distinct high-grade gliomas in L-2-hydroxyglutaric aciduria

Neuroimaging in cerebellar ataxia in childhood: A review

Ataxia is one of the most common pediatric movement disorders and can be caused by a large number of congenital and acquired diseases affecting the cerebellum or the vestibular or sensory system. It is mainly characterized by gait abnormalities, dysmetria, intention tremor, dysdiadochokinesia, dysarthria, and nystagmus. In young children, ataxia may manifest as the inability or refusal to walk. The diagnostic approach begins with a careful clinical history including the temporal evolution of ataxia and the inquiry of additional symptoms, is followed by a meticulous physical examination, and, depending on the results, is complemented by laboratory assays, electroencephalography, nerve conduction velocity, lumbar puncture, toxicology screening, genetic testing, and neuroimaging. Neuroimaging plays a pivotal role in either providing the final diagnosis, narrowing the differential diagnosis, or planning targeted further workup. In this review, we will focus on the most common form of ataxia in childhood, cerebellar ataxia (CA). We will discuss and summarize the neuroimaging findings of either the most common or the most important causes of CA in childhood or present causes of pediatric CA with pathognomonic findings on MRI. The various pediatric CAs will be categorized and presented according to (a) the cause of ataxia (acquired/disruptive vs. inherited/genetic) and (b) the temporal evolution of symptoms (acute/subacute, chronic, progressive, nonprogressive, and recurrent). In addition, several illustrative cases with their key imaging findings will be presented.

Clinico-radiological phenotyping and diagnostic pathways in childhood neurometabolic disorders-a practical introductory guide

Inborn errors of metabolism (IEM) although individually rare, together constitute a significant proportion of childhood neurological disorders. Majority of these disorders occur due to deficiency of an enzyme in a specific metabolic pathway, leading to damage by accumulation of a toxic substrate or deficiency of an essential metabolite. Early diagnosis is crucial in many of these conditions to prevent or minimise brain damage. Whilst many of the neuroimaging features are nonspecific, certain disorders demonstrate specific patterns due to selective vulnerability of different structures to different insults. Along with clinical and biochemical profile, neuroimaging thus plays a pivotal role in differentiating metabolic disorders from other causes, in providing a differential diagnosis or suggesting a metabolic pathway derangement, and on occasion also helps make a specific diagnosis. This allows initiation of targeted metabolic and genetic work up and treatment. Familiarity with the clinical features, relevant biochemical features and neuroimaging findings of common metabolic disorders to facilitate a prompt diagnosis cannot thus be overemphasized. In this article, we describe the latest classification scheme, the clinical and biochemical clues and common radiological patterns. The diagnostic algorithm followed in daily practice after clinico-radiological phenotyping is alluded to and illustrated by clinical vignettes. Focused sections on neonatal metabolic disorders and mitochondrial disorders are also provided. The purpose of this article is to provide a brief overview and serve as a practical primer to clinical and radiological phenotypes and diagnostic aspects of IEM.

Cerebral neoplasm in L-2-hydroxyglutaric aciduria: two different presentations

BACKGROUND

L-2-hydroxyglutaric aciduria (L2HGA) is a rare neurometabolic disorder characterized by a slowly progressive clinical course, psychomotor and mental retardation, macrocephaly, dysarthria, seizures, and cerebellar and extrapyramidal findings. The diagnosis depends on the presentation of increased levels of L-2-hydroxyglutaric acid in the urine, plasma, and cerebrospinal fluids. Patients with L2HGA have an increased risk for the development of cerebral neoplasms which, though rarely, can be the initial presentation of the disease. Moreover, patients with L2HGA have an increased risk for the development of cerebral neoplasms.

CASES PRESENTATION

Although psychomotor and mental retardation, macrocephaly, dysarthria, seizures, and cerebellar and extrapyramidal findings are the most common characteristics of the disease, we present two rare cases admitted with tumoral symptoms.

CONCLUSION

Patients with L2HGA have an increased risk for the development of cerebral neoplasms.

Neuroimaging Findings in Children with Constitutional Mismatch Repair Deficiency Syndrome

BACKGROUND AND PURPOSE

Constitutional mismatch repair deficiency is a hereditary childhood cancer predisposition syndrome characterized by brain tumors and colorectal and hematologic malignancies. Our objective was to describe the neuroimaging findings in patients with constitutional mismatch repair deficiency.

MATERIALS AND METHODS

This retrospective study included 14 children with genetically confirmed constitutional mismatch repair deficiency who were referred to 2 tertiary pediatric oncology centers.

RESULTS

Fourteen patients from 11 different families had diagnosed constitutional mismatch repair deficiency. The mean age at presentation was 9.3 years (range, 5-14 years). The most common clinical presentation was brain malignancy, diagnosed in 13 of the 14 patients. The most common brain tumors were glioblastoma (n = 7 patients), anaplastic astrocytoma (n = 3 patients), and diffuse astrocytoma (n = 3 patients). Nonspecific subcortical white matter T2 hyperintensities were noted in 10 patients (71%). Subcortical hyperintensities transformed into overt brain tumors on follow-up imaging in 3 patients. Additional non-neoplastic brain MR imaging findings included developmental venous anomalies in 12 patients (85%) and nontherapy-induced cavernous hemangiomas in 3 patients (21%).

CONCLUSIONS

On brain MR imaging, these patients have both highly characteristic intra-axial tumors (typically multifocal high-grade gliomas) and nonspecific findings, some of which might represent early stages of neoplastic transformation. The incidence of developmental venous anomalies is high in these patients for unclear reasons. Awareness of these imaging findings, especially in combination, is important to raise the suspicion of constitutional mismatch repair deficiency in routine diagnostic imaging evaluation or surveillance imaging studies of asymptomatic carriers because early identification of the phenotypic "gestalt" might improve outcomes.

The paradox of cancer genes in non-malignant conditions: implications for precision medicine

Next-generation sequencing has enabled patient selection for targeted drugs, some of which have shown remarkable efficacy in cancers that have the cognate molecular signatures. Intriguingly, rapidly emerging data indicate that altered genes representing oncogenic drivers can also be found in sporadic non-malignant conditions, some of which have negligible and/or low potential for transformation to cancer. For instance, activating KRAS mutations are discerned in endometriosis and in brain arteriovenous malformations, inactivating TP53 tumor suppressor mutations in rheumatoid arthritis synovium, and AKT, MAPK, and AMPK pathway gene alterations in the brains of Alzheimer's disease patients. Furthermore, these types of alterations may also characterize hereditary conditions that result in diverse disabilities and that are associated with a range of lifetime susceptibility to the development of cancer, varying from near universal to no elevated risk. Very recently, the repurposing of targeted cancer drugs for non-malignant conditions that are associated with these genomic alterations has yielded therapeutic successes. For instance, the phenotypic manifestations of CLOVES syndrome, which is characterized by tissue overgrowth and complex vascular anomalies that result from the activation of PIK3CA mutations, can be ameliorated by the PIK3CA inhibitor alpelisib, which was developed and approved for breast cancer. In this review, we discuss the profound implications of finding molecular alterations in non-malignant conditions that are indistinguishable from those driving cancers, with respect to our understanding of the genomic basis of medicine, the potential confounding effects in early cancer detection that relies on sensitive blood tests for oncogenic mutations, and the possibility of reverse repurposing drugs that are used in oncology in order to ameliorate non-malignant illnesses and/or to prevent the emergence of cancer.

The clinical use of IDH1 and IDH2 mutations in gliomas

Introduction: Mutations in the genes isocitrate dehydrogenase (IDH) 1 and 2 have been reported in a limited number of tumors. In gliomas, IDH mutations are primarily detected in WHO grade II-III tumors and represent a major biomarker with diagnostic, prognostic, and predictive implications. The recent development of IDH inhibitors and vaccines suggests that the IDH mutation is also an appealing target for therapy. Areas covered: This review focuses on the role of IDH mutations in diffuse gliomas. Besides discussing their role in gliomagenesis, we will emphasize the role of IDH mutations in clinical practice as a diagnostic, prognostic and predictive biomarker, and as a potential therapeutic target. Noninvasive detection of the IDH mutation by means of liquid biopsy and MR spectroscopy will also be discussed. Expert commentary: While IDH mutation is a consolidated diagnostic and prognostic biomarker in clinical practice, its role in oncogenesis is far from being elucidated, and there are several pending issues. The routine use of noninvasive techniques for detection and monitoring of the IDH status remains challenging. Although the IDH mutation is a very early alteration in gliomagenesis, it may then be omitted during tumor progression. This observation has important implications when designing targeted clinical trials.

Biochemical and Epigenetic Insights into L-2-Hydroxyglutarate, a Potential Therapeutic Target in Renal Cancer

PURPOSE

Elevation of L-2-hydroxylgutarate (L-2-HG) in renal cell carcinoma (RCC) is due in part to reduced expression of L-2-HG dehydrogenase (L2HGDH). However, the contribution of L-2-HG to renal carcinogenesis and insight into the biochemistry and targets of this small molecule remains to be elucidated.

EXPERIMENTAL DESIGN

Genetic and pharmacologic approaches to modulate L-2-HG levels were assessed for effects on in vitro and in vivo phenotypes. Metabolomics was used to dissect the biochemical mechanisms that promote L-2-HG accumulation in RCC cells. Transcriptomic analysis was utilized to identify relevant targets of L-2-HG. Finally, bioinformatic and metabolomic analyses were used to assess the L-2-HG/L2HGDH axis as a function of patient outcome and cancer progression.

RESULTS

L2HGDH suppresses both in vitro cell migration and in vivo tumor growth and these effects are mediated by L2HGDH's catalytic activity. Biochemical studies indicate that glutamine is the predominant carbon source for L-2-HG via the activity of malate dehydrogenase 2 (MDH2). Inhibition of the glutamine-MDH2 axis suppresses in vitro phenotypes in an L-2-HG-dependent manner. Moreover, in vivo growth of RCC cells with basal elevation of L-2-HG is suppressed by glutaminase inhibition. Transcriptomic and functional analyses demonstrate that the histone demethylase KDM6A is a target of L-2-HG in RCC. Finally, increased L-2-HG levels, L2HGDH copy loss, and lower L2HGDH expression are associated with tumor progression and/or worsened prognosis in patients with RCC.

CONCLUSIONS

Collectively, our studies provide biochemical and mechanistic insight into the biology of this small molecule and provide new opportunities for treating L-2-HG-driven kidney cancers.

Intraventricular Glioblastoma Multiforme in A Child with L2-Hydroxyglutaric Aciduria

L2-hydroxyglutaric aciduria (L2-HGA) is a rare neurometabolic disease characterized by accumulation of L2-hydroxyglutarate (L2-HG), a potential oncometabolite resulting in significant lifetime risk for cerebral tumors. Herein, we present a case of intraventricular glioblastoma multiforme (GBM) in a 16-year-old child with L2-HGA who presented with rapid functional decline and persistent vomiting. The tumor was completely resected, and the patient remained well at 2-year follow-up. Clinicians should be aware of the usual insidious nature of the disease. Rapid deterioration is unusual and should raise the suspicion of tumor development. This case also illustrates the importance of surveillance neuroimaging in patients with L2-HGA. To the best of our knowledge, only 1 case of GBM has been reported and it was sited in the temporal lobe, unlike the unusual intraventricular location in our case.

Isomers Identification of 2-hydroxyglutarate acid disodium salt (2HG) by Terahertz Time-domain Spectroscopy

2-Hydroxyglutaric acid disodium salt (2HG) is a unique biomarker existing in glioma, which can be used for recognizing cancer development stage and identifying the boundary between the ordinary tissue and cancer tissue. However, the most efficient detection method for 2HG now is Magnetic Resonance Spectroscopy (MRS), whose testing time is at least twenty minutes and the variability of 2HG (continuous synthesis and decomposition) determines it cannot be used as the real-time image in medical surgery. In this paper, by using the Terahertz Time-domain Spectroscopy (THz-TDS) System, we investigate the vibration spectra of 2HG isomers and further distinguish their physical properties by using Density Functional Theory. The differences between isomers are mainly attributed to the proton transfer inside the carbon chain. These results indicate that terahertz technology can identify the isomers of 2HG accurate and fast, which has important significance for the further investigation of glioma and clinical surgery.

The Enzymology of 2-Hydroxyglutarate, 2-Hydroxyglutaramate and 2-Hydroxysuccinamate and Their Relationship to Oncometabolites

Many enzymes make "mistakes". Consequently, repair enzymes have evolved to correct these mistakes. For example, lactate dehydrogenase (LDH) and mitochondrial malate dehydrogenase (mMDH) slowly catalyze the reduction of 2-oxoglutarate (2-OG) to the oncometabolite l-2-hydroxyglutarate (l-2-HG). l-2-HG dehydrogenase corrects this error by converting l-2-HG to 2-OG. LDH also catalyzes the reduction of the oxo group of 2-oxoglutaramate (2-OGM; transamination product of l-glutamine). We show here that human glutamine synthetase (GS) catalyzes the amidation of the terminal carboxyl of both the l- and d- isomers of 2-HG. The reaction of 2-OGM with LDH and the reaction of l-2-HG with GS generate l-2-hydroxyglutaramate (l-2-HGM). We also show that l-2-HGM is a substrate of human ω-amidase. The product (l-2-HG) can then be converted to 2-OG by l-2-HG dehydrogenase. Previous work showed that 2-oxosuccinamate (2-OSM; transamination product of l-asparagine) is an excellent substrate of LDH. Finally, we also show that human ω-amidase converts the product of this reaction (i.e., l-2-hydroxysuccinamate; l-2-HSM) to l-malate. Thus, ω-amidase may act together with hydroxyglutarate dehydrogenases to repair certain "mistakes" of GS and LDH. The present findings suggest that non-productive pathways for nitrogen metabolism occur in mammalian tissues in vivo. Perturbations of these pathways may contribute to symptoms associated with hydroxyglutaric acidurias and to tumor progression. Finally, methods for the synthesis of l-2-HGM and l-2-HSM are described that should be useful in determining the roles of ω-amidase/4- and 5-C compounds in photorespiration in plants.

Childhood cancer predisposition syndromes-A concise review and recommendations by the Cancer Predisposition Working Group of the Society for Pediatric Oncology and Hematology

Heritable predisposition is an important cause of cancer in children and adolescents. Although a large number of cancer predisposition genes and their associated syndromes and malignancies have already been described, it appears likely that there are more pediatric cancer patients in whom heritable cancer predisposition syndromes have yet to be recognized. In a consensus meeting in the beginning of 2016, we convened experts in Human Genetics and Pediatric Hematology/Oncology to review the available data, to categorize the large amount of information, and to develop recommendations regarding when a cancer predisposition syndrome should be suspected in a young oncology patient. This review summarizes the current knowledge of cancer predisposition syndromes in pediatric oncology and provides essential information on clinical situations in which a childhood cancer predisposition syndrome should be suspected.

Clinical features and disease progression of L-2-hydroxyglutaric aciduria in 27 Staffordshire bull terriers

To describe the development of clinical signs (CS) and outcome of L-2-hydroxyglutaric aciduria (L-2-HGA), owners of 119 Staffordshire bull terriers positive for the known L-2-hydroxyglutarate dehydrogenase autosomal-recessive mutations were requested to complete a questionnaire regarding their pet's CS. Questionnaires were returned for 27 dogs, all with neurological abnormalities-not all questions were answered in all cases. The mean age of CS onset was 12 months (range 2.5-60). Gait dysfunction was reported in 26/26 dogs, with stiffness of all four limbs the most common (24/26) and earliest recognised abnormality. Kyphosis (19/26), body and/or head tremors (19/26) and hypermetria (15/26) were frequent. Behavioural changes were present in 24/27 dogs; most commonly staring into space (21/24), signs of dementia (17/24) and loss of training (15/24). Eighteen dogs demonstrated paroxysmal seizure-like/dyskinetic episodes. Nineteen (70 per cent) dogs were alive at a mean survival time of 76.6 months (12-170) after onset of CS. L-2-HGA was the cause of euthanasia in six dogs. Euthanasia occurred at a mean survival time of 44 months (8.5-93) after onset of CS, with 2/8 dogs euthanased within 12 months. L-2-HGA is considered a progressive neurological disease; however, CS can be successfully managed with affected dogs potentially living a normal lifespan.

Expression of Idh1R132H in the Murine Subventricular Zone Stem Cell Niche Recapitulates Features of Early Gliomagenesis

Isocitrate dehydrogenase 1 mutations drive human gliomagenesis, probably through neomorphic enzyme activity that produces D-2-hydroxyglutarate. To model this disease, we conditionally expressed Idh1R132H in the subventricular zone (SVZ) of the adult mouse brain. The mice developed hydrocephalus and grossly dilated lateral ventricles, with accumulation of 2-hydroxyglutarate and reduced α-ketoglutarate. Stem and transit amplifying/progenitor cell populations were expanded, and proliferation increased. Cells expressing SVZ markers infiltrated surrounding brain regions. SVZ cells also gave rise to proliferative subventricular nodules. DNA methylation was globally increased, while hydroxymethylation was decreased. Mutant SVZ cells overexpressed Wnt, cell-cycle and stem cell genes, and shared an expression signature with human gliomas. Idh1R132H mutation in the major adult neurogenic stem cell niche causes a phenotype resembling gliomagenesis.

MRI features in 17 patients with l2 hydroxyglutaric aciduria

l-2-Hydroxyglutaric (l-2-HG) aciduria is a rare inherited metabolic disease usually observed in children. Patients present a very slowly progressive deterioration with cerebellar ataxia, mild or severe mental retardation, and various other clinical signs including extrapyramidal and pyramidal symptoms, and seizures Goffette et al. [1]. This leukencephalopathy was first described in 1980 Duran et al. [2]. Brain magnetic resonance imaging (MRI) demonstrates nonspecific subcortical white matter (WM) loss, cerebellar atrophy and changes in dentate nuclei and putamen Steenweg et al. [3]. The diagnosis is highlighted by increased levels of l-2-HG in body fluids such as urine and cerebrospinal fluid.

The purpose of this study is to retrospectively describe the brain MRI features in l-2-HG aciduria.

Diffusely infiltrating astrocytomas: pathology, molecular mechanisms and markers

Diffusely infiltrating astrocytomas include diffuse astrocytomas WHO grade II and anaplastic astrocytomas WHO grade III and are classified under astrocytic tumours according to the current WHO Classification. Although the patients generally have longer survival as compared to those with glioblastoma, the timing of inevitable malignant progression ultimately determines the prognosis. Recent advances in molecular genetics have uncovered that histopathologically diagnosed astrocytomas may consist of two genetically different groups of tumours. The majority of diffusely infiltrating astrocytomas regardless of WHO grade have concurrent mutations of IDH1 or IDH2, TP53 and ATRX. Among these astrocytomas, no other genetic markers that may distinguish grade II and grade III tumours have been identified. Those astrocytomas without IDH mutation tend to have a distinct genotype and a poor prognosis comparable to that of glioblastomas. On the other hand, diffuse astrocytomas that arise in children do not harbour IDH/TP53 mutations, but instead display mutations of BRAF or structural alterations involving MYB/MYBL1 or FGFR1. A molecular classification may thus help delineate diffusely infiltrating astrocytomas into distinct pathogenic and prognostic groups, which could aid in determining individualised therapeutic strategies.