GLUT-1DS resistant to ketogenic diet: from clinical feature to in silico analysis. An exemplificative case report with a literature review.

Glucose transporter type 1 deficiency syndrome (GLUT-1DS) is characterized by alterations in glucose translocation through the blood-brain barrier (BBB) due to mutation involving the GLUT-1 transporter. The fundamental therapy is ketogenic diet (KD) that provide an alternative energetic substrate - ketone bodies that across the BBB via MCT-1 - for the brain. Symptoms are various and include intractable seizure, acquired microcephalia, abnormal ocular movement, movement disorder, and neurodevelopment delay secondary to an energetic crisis for persistent neuroglycopenia. KD is extremely effective in controlling epileptic seizures and has a positive impact on movement disorders and cognitive impairment. Cases of KD resistance are rare, and only a few of them are reported in the literature, all regarding seizure. Our study describes a peculiar case of GLUT-1DS due to a new deletion involving the first codon of SLC2A1 gene determining a loss of function with a resistance to KD admitted to hospital due to intractable episodes of dystonia. This patient presented a worsening of symptomatology at higher ketonemia values but without hyperketosis and showed a complete resolution of symptomatology while maintaining low ketonemia values. Our study proposes an in-silico genomic and proteomic analysis aimed at explaining the atypical response to KD exhibited by our patient. In this way, we propose a new clinical and research approach based on precision medicine and molecular modelling to be applied to patients with GLUT-1DS resistant to first-line treatment with ketogenic diet by in silico study of genetic and altered protein product.

The clinical and biochemical hallmarks generally associated with GLUT1DS may be caused by defects in genes other than SLC2A1.

Glucose transporter 1 deficiency syndrome (GLUT1DS) is a neurometabolic disorder caused by haploinsufficiency of the GLUT1 glucose transporter (encoded by SLC2A1) leading to defective glucose transport across the blood-brain barrier. This work describes the genetic analysis of 56 patients with clinical or biochemical GLUT1DS hallmarks. 55.4% of these patients had a pathogenic variant of SLC2A1, and 23.2% had a variant in one of 13 different genes. No pathogenic variant was identified for the remaining patients. Expression analysis of SLC2A1 indicated a reduction in SLC2A1 mRNA in patients with pathogenic variants of this gene, as well as in one patient with a pathogenic variant in SLC9A6, and in three for whom no candidate variant was identified. Thus, the clinical and biochemical hallmarks generally associated with GLUT1DS may be caused by defects in genes other than SLC2A1.

The effect of chronic neuroglycopenia on resting state networks in GLUT1 syndrome across the lifespan.

Glucose transporter type I deficiency syndrome (GLUT1DS) is an encephalopathic disorder due to a chronic insufficient transport of glucose into the brain. PET studies in GLUT1DS documented a widespread cortico-thalamic hypometabolism and a signal increase in the basal ganglia, regardless of age and clinical phenotype. Herein, we captured the pattern of functional connectivity of distinct striatal, cortical, and cerebellar regions in GLUT1DS (10 children, eight adults) and in healthy controls (HC, 19 children, 17 adults) during rest. Additionally, we explored for regional connectivity differences in GLUT1 children versus adults and according to the clinical presentation. Compared to HC, GLUT1DS exhibited increase connectivity within the basal ganglia circuitries and between the striatal regions with the frontal cortex and cerebellum. The excessive connectivity was predominant in patients with movement disorders and in children compared to adults, suggesting a correlation with the clinical phenotype and age at fMRI study. Our findings highlight the primary role of the striatum in the GLUT1DS pathophysiology and confirm the dependency of symptoms to the patients' chronological age. Despite the reduced chronic glucose uptake, GLUT1DS exhibit increased connectivity changes in regions highly sensible to glycopenia. Our results may portrait the effect of neuroprotective brain strategy to overcome the chronic poor energy supply during vulnerable ages.

Glucose transporter type 1 deficiency syndrome and the ketogenic diet.

Glucose transporter type 1 deficiency syndrome (GLUT1DS) is characterised by deficient glucose transport over the blood-brain barrier and reduced glucose availability in the brain. This causes epilepsy, movement disorders, and cognitive impairment. Treatment with ketogenic diet provides ketones as alternative energy source. However, not all GLUT1DS patients are on dietary treatment (worldwide registry: 77/181 [43%] of patients). The current 25-year experience allows evaluation of effects and tolerability of dietary treatment for GLUT1DS. To this end, literature was searched up to January 2019 for individual case reports and series reporting (side) effects of dietary treatment for GLUT1DS. Upon aggregation of data for analysis, we identified 270 GLUT1DS patients with dietary treatment with a mean follow-up of 53 months. Epilepsy improved for 83% of 230 patients and remained unchanged for 17%, movement disorders improved for 82% of 127 patients and remained unchanged for 17%, and cognition improved for 59% of 58 patients and remained stable for 40%. Effects on epilepsy were seen within days/weeks and were most pronounced in patients with early treatment initiation. Effects on movement disorders were noticed within months and were strongest in patients with higher cerebrospinal fluid-to-blood glucose ratio. Although side effects were minimal, 18% of 270 patients reported poor compliance. In individual patients, symptoms deteriorated upon low ketosis, poor compliance, or treatment discontinuation. Based on the good tolerability and strong favourable effect of dietary treatment on GLUT1DS symptoms, we advocate dietary treatment in all GLUT1DS patients and prompt diagnosis or screening to allow early treatment.

Gene therapy for Glut1-deficient mouse using an adeno-associated virus vector with the human intrinsic GLUT1 promoter.

BACKGROUND: We generated an adeno-associated virus (AAV) vector in which the human SLC2A1 gene, encoding glucose transporter type 1 (GLUT1), was expressed under the human endogenous GLUT1 promoter (AAV-GLUT1). We examined whether AAV-GLUT1 administration could lead to functional improvement in GLUT1-deficient mice. METHODS: We extrapolated human endogenous GLUT1 promoter sequences from rat minimal Glut1 promoter sequences. We generated a tyrosine-mutant AAV9/3 vector in which human SLC2A1-myc-DDK was expressed under the human GLUT1 promoter (AAV-GLUT1). AAV-GLUT1 was administered to GLUT1-deficient mice (GLUT1+/- mice) via intracerebroventricular injection (1.85 × 1010 vg/mouse or 6.5 × 1010 vg/mouse). We analyzed exogenous GLUT1 mRNA and protein expression in the brain and other major organs. We also examined improvements of cerebral microvasculature, motor function using rota-rod and footprint tests, as well as blood and cerebrospinal fluid (CSF) glucose levels. Additionally, we confirmed exogenous GLUT1 protein distribution in the brain and other organs after intracardiac injection (7.8 × 1011 vg/mouse). RESULTS: Exogenous GLUT1 protein was strongly expressed in the cerebral cortex, hippocampus and thalamus. It was mainly expressed in endothelial cells, and partially expressed in neural cells and oligodendrocytes. Motor function and CSF glucose levels were significantly improved following intracerebroventricular injection. Exogenous GLUT1 expression was not detected in other organs after intracerebroventricular injection of AAV-GLUT1, whereas it was detected in the liver and muscle tissue after intracardiac injection. CONCLUSIONS: Exogenous GLUT1 expression after AAV-GLUT1 injection approximated that of physiological human GLUT1 expression. Local central nervous system administration of AAV-GLUT1 improved CSF glucose levels and motor function of GLUT1-deficient mice and minimized off-target effects.

The changing face of dietary therapy for epilepsy.

UNLABELLED: Ketogenic diet is an established and effective non-pharmacologic treatment for drug-resistant epilepsy. Ketogenic diet represents the treatment of choice for GLUT-1 deficiency syndrome and pyruvate dehydrogenase complex deficiency. Infantile spasms, Dravet syndrome and myoclonic-astatic epilepsy are epilepsy syndromes for which ketogenic diet should be considered early in the therapeutic pathway. Recently, clinical indications for ketogenic diet have been increasing, as there is emerging evidence regarding safety and effectiveness. Specifically, ketogenic diet response has been investigated in refractory status epilepticus and encephalopathy with status epilepticus during sleep. New targets in neuropharmacology, such as mitochondrial permeability transition, are being studied and might lead to using it effectively in other neurological diseases. But, inefficient connectivity and impaired ketogenic diet proposal limit ideal availability of this therapeutic option. Ketogenic diet in Italy is not yet considered as standard of care, not even as a therapeutic option for many child neurologists and epileptologists. CONCLUSIONS: The aim of this review is to revisit ketogenic diet effectiveness and safety in order to highlight its importance in drug-resistant epilepsy and other neurological disorders. WHAT IS KNOWN: • Ketogenic diet efficacy is now described in large case series, with adequate diet compliance and side effects control. • Ketogenic diet is far from being attempted as a first line therapy. Its availability varies worldwide. What is New: • New pharmacological targets such as mitochondrial permeability transition and new epileptic syndromes and etiologies responding to the diet such as refractory status epilepticus are being pointed out. • Ketogenic diet can function at its best when used as a tailor-made therapy. Fine tuning is crucial.

Mutational and functional analysis of Glucose transporter I deficiency syndrome.

OBJECTIVE: We investigated a correlation between a mutation in the SLC2A1 gene and functional disorders in Glucose transporter I deficiency syndrome (GLUT1DS). METHODS: We performed direct sequence analysis of SLC2A1 in a severe GLUT1DS patient and identified a novel frame shift mutation, c.906_907insG, p.V303fs. We created a plasmid vector carrying the c.906_907insG mutation, as well as A405D or R333W in the SLC2A1, which are found in patients with mild and moderate GLUT1DS severity, respectively. We transiently expressed these mutants and wild type SLC2A1 plasmids in a human embryonic kidney cell line (HEK293), and performed immunoblotting, immunofluorescence, and enzymatic photometric 2-deoxyglucose (2DG) uptake assays. RESULTS: GLUT1 was not detected after transient expression of the SLC2A1 plasmid carrying c.906_907insG by either immunoblotting or immunofluorescence. The degree of glucose transport reduction as determined by enzymatic photometric 2DG assay uptake correlated with disease severity. CONCLUSIONS: Enzymatic photometric 2DG uptake study appears to be a suitable functional assay to predict the effect of SLC2A1 mutations on GLUT1 transport.

Does ketogenic diet improve cognitive function in patients with GLUT1-DS? A 6- to 17-month follow-up study.

The aim of this study was to investigate the effects of ketogenic diet (KD) on cognitive function in patients with glucose transporter protein 1 deficiency syndrome (GLUT1-DS). Six patients with GLUT1-DS who were referred to the National Centre for Epilepsy in Norway during the period of November 2011-September 2013 were included. They were diagnosed with GLUT1-DS on the basis of early-onset seizures and developmental delay (with or without movement disorders or microcephaly) in addition to CSF-to-blood glucose ratio below 0.5. They were all treated with either classical KD or modified Atkins diet (MAD). The effect of the diet with >90% reduction in the seizure frequency was, in retrospect, considered as a support for the diagnosis. The patients underwent standardized neuropsychological assessment before the diet was initiated, and they were reassessed after a minimum of six months on the diet. The neuropsychological tests were individually selected for each patient in order to match their cognitive level. The main finding was a considerable improvement in several aspects of neuropsychological functioning after 6-17 months of dietary treatment in all the six patients. The greatest progress was seen in the youngest children. Our findings suggest that early diagnosis and dietary treatment are important in order to prevent developmental delay. However, also adults with GLUT1-DS may profit from dietary treatment by improving alertness, setting the stage for enhanced learning capacity, as well as physical endurance and quality of life.

Occurrence of GLUT1 deficiency syndrome in patients treated with ketogenic diet.

Glucose transporter 1 deficiency syndrome (GLUT1-DS) is a treatable metabolic encephalopathy caused by a mutation in the SLC2A1 gene. This mutation causes a compromised transport of glucose across the blood-brain barrier. The treatment of choice is ketogenic diet, with which most patients become seizure-free. At the National Centre for Epilepsy, we have, since 2005, offered treatment with ketogenic diet (KD) and modified Atkins diet (MAD) to children with difficult-to-treat epilepsy. As we believe many children with GLUT1-DS are unrecognized, the aim of this study was to search for patients with GLUT1-DS among those who had been responders (>50% reduction in seizure frequency) to KD or MAD. Of the 130 children included, 58 (44%) were defined as responders. Among these, 11 were already diagnosed with GLUT1-DS. No mutations in the SLC2A1 gene were detected in the remaining patients. However, the clinical features of these patients differed considerably from the patients diagnosed with GLUT1-DS. While 9 out of 10 patients with GLUT1-DS became seizure-free with dietary treatment, only 3 out of the 33 remaining patients were seizure-free with KD or MAD treatment. We therefore conclude that a seizure reduction of >50% following dietary treatment is not a suitable criterion for identifying patients with GLUT1-DS, as these patients generally achieve complete seizure freedom shortly after diet initiation.

GLUT1DS focus on dysarthria.

RESEARCH PURPOSE: GLUT1 deficiency syndrome (GLUT1DS) is a rare genetic disorder caused by a mutation in the SLC2A1 gene that limits the transport of glucose across the blood-brain barrier. Speech disorders and dysarthria are typical findings in patients with GLUT1DS, but have never been deeply phenotyped. The aim of the present study was to characterize speech abilities in a sample of patients with GLUT1DS. RESULTS: 30 patients with GLUT1DS were recruited. We reported impairments in different speech and oromotor domains: the speech was characterized by dysarthria, inaccurate articulation of consonants, abnormal nasal resonance, errors in intonation and prosody and low intelligibility. We observed difficulties in motor planning and programming. Moreover, we observed a significant difference between the dysarthric level of impairment with genotype groups. CONCLUSIONS: The presence of a speech disorder in patients with GLUT1DS represents a core feature of the syndrome. Our findings suggest that patients with GLUT1DS would benefit from a comprehensive neurocognitive assessment to detect strengths and weaknesses of the speech profile. Understanding the speech and language phenotype in GLUT1DS is critical for planning early intervention to positively influence the global development of patients with GLUT1DS.

Role of EEG as a monitoring tool in patients with glucose transporter type I deficiency syndrome (GLUT1-DS) on ketogenic diet.

RATIONALE: Glucose transporter type I deficiency syndrome (GLUT1-DS) is the fourth most frequent single-gene epilepsy refractory to standard antiepileptic drugs. Multiple seizure types and variable electrographic findings are reported. Ketogenic diet is expected to result in the complete resolution of the epileptiform activity. METHODS: A retrospective chart review of patients with GLUT1-DS on ketogenic diet between December 2012 and February 2022 was done. Analysis of the EEGs prior to and during the ketogenic diet was done. RESULTS: 34 patients on ketogenic diet were reviewed. Ten had clinical diagnosis of GLUT1-DS, and seven of them had genetic confirmation. 71% were female. The average age at seizure onset was 13.85 m.o. (range: 3-60, SD ±20.52), at diagnosis was 44.57 m.o (range: 19-79), and at the onset of ketogenic diet was 46.43 m.o. (range: 20-83). 29 months (range: 13-38) delay between symptoms onset until diagnosis was noticed. At the diagnosis 100% reported seizures: 71% myoclonic, 57% generalized motor, 57% absence, 28% atonic, and 14% focal motor. Also, 71% abnormal eye movements, 57% ataxia, and 28% intolerance to fasting. 86% had normal brain MRI. 71% had abnormal EEG. All were on ketogenic diet, and four on classical (1.75:1-2.25:1 ratio). Six were clinically seizure-free after the ketogenic diet. EEG features included notch delta, focal spike and wave, and generalized spike/polyspike and wave. One patient had bilateral independent centrotemporal spikes. Spikes showed high and very high amplitude in all of them (>200 µV). The variation of the spike index decreased in three patients but increased in two. CONCLUSION: Ketogenic diet is the choice treatment for patients with GLUT1-DS. Electrographic features could show worsening after initiation of the ketogenic diet even with seizure control. EEG did not prove to be a reliable tool for adjusting KD in our cohort. Centrotemporal spikes have not been reported in patients with GLUT-1 DS.

Uncommon use of intermittent glucose administration for infrequent non-epileptic paroxysmal events in GLUT1-DS.

The ketogenic diet is the treatment of GLUT1 deficiency syndrome that provides an alternative energy source for the brain. However, there are some limitations, including compliance issues as well as patients who do not respond to the ketogenic diet. We report the case of two patients that were not on any particular diet. Both experienced infrequent paroxysmal non-epileptic events (acute ataxia and exercise-induced dystonia). Intermittent glucose intake prior to physical activity for exercise-induced symptoms and at the onset of symptoms for acute ataxia showed consistent and reproducible improvement of the symptoms. Our observations raised the question of developing a new treatment strategy with the induction of a sustained increase in blood glucose. For now, the use of this strategy should be limited to a small group of GLUT1-DS patients who are not on a ketogenic diet.

Ketonemia variability through menstrual cycle in patients undergoing classic ketogenic diet.

Introduction: Ketogenic dietary therapies (KDT) are well-established, safe, non-pharmacologic treatments used for children and adults with drug-resistant epilepsy and other neurological disorders. Ketone bodies (KBs) levels are recognized as helpful to check compliance to the KDT and to attempt titration of the diet according to the individualized needs. KBs might undergo inter-individual and intra-individual variability and can be affected by several factors. Possible variations in glycemia and ketone bodies blood levels according to the menstrual cycle have not been systematically assessed yet, but this time window deserves special attention because of hormonal and metabolic related changes. Methods: This study aims at searching for subtle changes in KBs blood level during menstrual cycle in female patients undergoing a stable ketogenic diet, by analyzing 3-months daily measurement of ketone bodies blood levels and glucose blood levels throughout the menstrual cycle. Results: We report the preliminary results on six female patients affected by GLUT1DS or drug resistant epilepsy, undergoing a stable classic ketogenic diet. A significant increase in glucose blood levels during menstruation was found in the entire cohort. As far as the ketone bodies blood levels, an inversely proportional trend compared to glycemia was noted. Conclusion: Exploring whether ketonemia variations might occur according to the menstrual cycle is relevant to determine the feasibility of transient preventive diet adjustments to assure a continuative treatment efficacy and to enhance dietary behavior support. Clinical trial registration: clinicaltrials.gov, identifier NCT05234411.

Timing of Ketogenic Dietary Therapy (KDT) Introduction and Its Impact on Cognitive Profiles in Children with Glut1-DS-A Preliminary Study.

The aim of this research was to characterize cognitive abilities in patients with Glut1-Deficiency syndrome (Glut1DS) following ketogenic diet therapy (KDT). METHODS: The cognitive profiles of eight children were assessed using the Wechsler Intelligence Scale (WISC-IV). The effect of ketogenic diet therapy (KDT) on individual subareas of intelligence was analyzed considering the potential influence of speech motor impairments. RESULTS: Patients with Glut1DS showed a wide range of cognitive performance levels. Some participants showed statistically and clinically significant discrepancies between individual subdomains of intelligence. Both variables, KDT initiation as well as duration, had a positive effect on the overall IQ score. Significant correlations were partially found between the time of KDT initiation and the level of IQ scores, depending on the presence of expressive language test demands of the respective subtests of the WISC-IV. Accordingly, the participants benefited les in the linguistic cognitive domain. The discrepancies in cognitive performance profiles of patients with Glut1DS can be attributed to the possibility of a negative distortion of the results due to the influence of speech motor impairments. CONCLUSIONS: The individual access skills of test persons should be more strongly considered in test procedures for the assessment of intelligence to reduce the negative influence of motor deficits on test performance. Specific characterization and systematization of the speech disorder are indispensable for determining the severity of speech motor impairment in Glut1DS. Therefore, a stronger focus on dysarthria during diagnosis and therapy is necessary.

Case report: KETOLAND the psychoeducation program for ketogenic diet.

Glucose transporter type 1 deficiency syndrome (GLUT1DS) is a rare neurological disorder characterized by a wide spectrum of symptoms: epilepsy, movement disorders and neurocognitive impairment. The gold standard treatment for GLUT1DS are ketogenic dietary therapies (KDTs), specifically classical ketogenic diet (CKD). Despite the benefits, CKD often represents a challenge for patients and their families since meal preparation is extremely demanding and deviates a lot from normal diet. To assure an optimal compliance to CKD a psychological support for parents and patients with GLUT1DS is highly recommended. Specifically, a psychoeducational intervention that ameliorates the knowledge about the illness and its therapy improves treatment' s adherence and efficacy. The aim of this case report is to investigate the effectiveness of a psychoeducational program, partially implemented through telepsychology, based on the theoretical model of Cognitive Behavioral Play Therapy (CBPT) to support KDT knowledge and adherence in a patient with GLUT1DS who presented a worsening of her clinical picture due to a sparse knowledge of KDTs principles which determined a low adherence. Thus, with this case report we propose a model of intervention with psychoeducation in a patient with a complex chronic disease.

Establishment of a flow cytometry screening method for patients with glucose transporter 1 deficiency syndrome.

Objective: We assessed the usefulness of flow cytometry as a functional assay to measure glucose transporter 1 (GLUT1) levels on the surface of red blood cells (RBCs) from Japanese patients with glucose transporter 1 deficiency syndrome (Glut1DS). Methods: We recruited 13 genetically confirmed Glut1DS patients with a solute carrier family 2 member 1 (SLC2A1) mutation (eight missense, one frameshift, two nonsense, and two deletion) and one clinically suspected Glut1DS-like patient without an SLC2A1 mutation, and collected whole blood with informed consent. We stained pelleted RBCs (1 µL) from the patients with a Glut1.RBD ligand and anti-glycophorin A antibody, which recognizes a human RBC membrane protein, and analyzed the cells using flow cytometry. Results: Relative GLUT1 levels quantified by flow cytometry in 11 of 13 patients with definite Glut1DS were 90% below those of healthy controls. Relative GLUT1 levels were not reduced in two of 13 Glut1DS patients who had a missense mutation and no intellectual disability and one Glut1DS-like patient without an SLC2A1 mutation. Relative GLUT1 levels were significantly reduced in Glut1DS patients with an SLC2A1 mutation, more severe intellectual disability, and spasticity. Conclusions: This method to detect GLUT1 levels on RBCs is simple and appears to be an appropriate screening assay to identify severe Glut1DS patients in the early stage before the development of irreversible neurologic damage caused by chronic hypoglycorrhachia.

Glut1 deficiency syndrome throughout life: clinical phenotypes, intelligence, life achievements and quality of life in familial cases.

BACKGROUND: Glut1 deficiency syndrome (Glut1-DS) is a rare metabolic encephalopathy. Familial forms are poorly investigated, and no previous studies have explored aspects of Glut1-DS over the course of life: clinical pictures, intelligence, life achievements, and quality of life in adulthood. Clinical, biochemical and genetic data in a cohort of familial Glut1-DS cases were collected from medical records. Intelligence was assessed using Raven's Standard Progressive Matrices and Raven's Colored Progressive Matrices in adults and children, respectively. An ad hoc interview focusing on life achievements and the World Health Organization Quality of Life Questionnaire were administered to adult subjects. RESULTS: The clinical picture in adults was characterized by paroxysmal exercise-induced dyskinesia (PED) (80%), fatigue (60%), low intelligence (60%), epilepsy (50%), and migraine (50%). However, 20% of the adults had higher-than-average intelligence. Quality of Life (QoL) seemed unrelated to the presence of PED or fatigue in adulthood. An association of potential clinical relevance, albeit not statistically significant, was found between intelligence and QoL. The phenotype of familial Glut1-DS in children was characterized by epilepsy (83.3%), intellectual disability (50%), and PED (33%). CONCLUSION: The phenotype of familial Glut1-DS shows age-related differences: epilepsy predominates in childhood; PED and fatigue, followed by epilepsy and migraine, characterize the condition in adulthood. Some adults with familial Glut1-DS may lead regular and fulfilling lives, enjoying the same QoL as unaffected individuals. The disorder tends to worsen from generation to generation, with new and more severe symptoms arising within the same family. Epigenetic studies might be useful to assess the phenotypic variability in Glut1-DS.

Characterization of Speech and Language Phenotype in GLUT1DS.

BACKGROUND: To analyze the oral motor, speech and language phenotype in a sample of pediatric patients with GLUT 1 transporter deficiency syndrome (GLUT1DS). METHODS: eight Italian-speaking children with GLUT1DS (aged 4.6-15.4 years) in stable treatment with ketogenic diet from a variable time underwent a specific and standardized speech and language assessment battery. RESULTS: All patients showed deficits with different degrees of impairment in multiple speech and language areas. In particular, orofacial praxis, parallel and total movements were the most impaired in the oromotor domain; in the speech domain patients obtained a poor performance in the diadochokinesis rate and in the repetition of words that resulted as severely deficient in seven out of eight patients; in the language domain the most affected abilities were semantic/phonological fluency and receptive grammar. CONCLUSIONS: GLUT1DS is associated to different levels of speech and language impairment, which should guide diagnostic and therapeutic intervention. Larger population data are needed to identify more precisely a speech and language profile in GLUT1DS patients.

A Family With a Complex Phenotype Caused by Two Different Rare Metabolic Disorders: GLUT1 and Very-Long-Chain Fatty Acid Dehydrogenase (VLCAD) Deficiencies.

GLUT1 Deficiency Syndrome (GLUT1-DS) is a rare and potentially treatable neurometabolic condition, caused by a reduced glucose transport into the brain and clinically characterized by an epileptic encephalopathy with movement disorders. A wide inter-intrafamilial phenotypic variability has been reported. Very-long-chain acyl-CoA dehydrogenase (VLCAD) deficiency is an inherited metabolic disorder of mitochondrial long-chain fatty acid oxidation (FAO) with also a variable age of onset and clinical presentation including cardiomyopathy, hypoketotic hypoglycemia, and liver disease. Sometimes, VLCAD manifests later with a prevalent muscle involvement characterized by exercise intolerance and recurrent rhabdomyolysis. We report a 40-year-old man with mild mental retardation and sporadic choreo-athetoid movements, who complained of recurrent episodes of rhabdomyolysis triggered by exercise or fasting since his twenties. His 15-year-old son had a psychomotor developmental delay with episodes of drowsiness mainly at fasting and exercise-induced choreo-athetoid movements but no history of pigmenturia. Clinical and laboratory findings in the son suggested a diagnosis of GLUT1-DS confirmed by SCL2A1 genetic analysis that revealed a heterozygous mutation c.997C>T (p.R333W) that was also found in the proband. However, the presence in the latter of recurrent exercise-induced rhabdomyolysis, never reported in GLUT1-DS, implied a second metabolic disorder. Increased plasma C14:1-carnitine levels and the identification of two known heterozygous mutations c. 553G>A (p.G185S) and c.1153C>T (p.R385W) in ACADVL confirmed the additional diagnosis of VLCAD deficiency in the proband. Nowadays, there is an increasing evidence of "double trouble" cases of genetic origin. Consequently, when atypical features accompany a known phenotype, associated comorbidities should be considered.

A Challenging Diagnosis of Atypical Glut1-DS: A Case Report and Literature Review.

Glucose transporter type 1 deficiency syndrome (Glut1-DS) is a rare neurometabolic disorder caused by mutations of the SLC2A1 gene. Paroxysmal exercise-induced dyskinesia is regarded as a representative symptom of Glut1-DS. Paroxysmal non-kinesigenic dyskinesia is usually caused by aberrations of the MR1 and KCNMA1 genes, but it also appears in Glut1-DS. We herein document a patient with Glut1-DS who suffered first from paroxysmal exercise-induced dyskinesia and subsequently paroxysmal non-kinesigenic dyskinesia and experienced a recent worsening of symptoms accompanied with a low fever. The lumbar puncture result showed a decreased glucose concentration and increased white blood cell (WBC) count in cerebrospinal fluid (CSF). The exacerbated symptoms were initially suspected to be caused by intracranial infection due to a mild fever of <38.0°C, decreased CSF glucose, and increased CSF WBC count. However, the second lumbar puncture result indicated a decreased glucose concentration and normal WBC count in CSF with no anti-infective agents, and the patient's symptoms were not relieved apparently. The continuous low glucose concentration attracted our attention, and gene analysis was performed. According to the gene analysis result, the patient was diagnosed with Glut1-DS finally. This case indicates that the complex paroxysmal dyskinesia in Glut1-DS may be confusing and pose challenges for accurate diagnosis. Except intracranial infection, Glut1-DS should be considered as a differential diagnosis upon detection of a low CSF glucose concentration and dyskinesia. The case presented here may encourage clinicians to be mindful of this atypical manifestation of Glut1-DS in order to avoid misdiagnosis.