Long-term clinical course of Glut1 deficiency syndrome

10 patients, 10 years - Long term follow-up of cardiovascular risk factors in Glut1 deficiency treated with ketogenic diet therapies: A prospective, multicenter case series

BACKGROUND AND AIMS

Glut1 Deficiency (Glut1D) is caused by impaired glucose transport into brain. The resulting epileptic encephalopathy and movement disorders can be treated effectively by high-fat carbohydrate-restricted ketogenic diet therapies (KDT) mimicking fasting and providing ketones as an alternative cerebral fuel. Recently 6-24 months follow-ups of epileptic patients reported elevated blood lipids and intima thickening of the carotid artery raising concerns about potential cardiovascular risks by KDT. To clarify potential cardiovascular risks we performed a prospective 10 year follow up of 10 Glut1D patients.

METHODS

Between August 2001 and January 2016 we enrolled Glut1D patients on KDT at two hospitals in Germany in this prospective, multicenter case series. The minimal follow up was 10 years. Standard deviation scores (SDS) of body mass index (BMI), total cholesterol (TC), HDL-/LDL cholesterol, and triglycerides (TG) before initiation of KDT were compared with respective values at 6 months, 2, 5 years, and 10 years after initiation. After 10 years on KDT cardiovascular risk, assessed by BMI, carotid intima-media thickness (CIMT) measurement, and blood pressure, was compared to a healthy reference population (n = 550).

RESULTS

Baseline and 10 year follow-up investigations were available for 10 individuals with Glut1D on KDT. After two years on KDT BMI increased significantly, while total cholesterol, HDL-cholesterol, and LDL-cholesterol decreased. Within 3-5 years on KDT these differences disappeared, and after 10 years blood lipid parameters reflected the situation at initiation of KDT. Prior to KDT one child had dyslipidaemia, but no child after 10 years on KDT. No significant differences were observed with respect to BMI SDS (p = 0.26), CIMT (p = 0.63) or systolic and diastolic blood pressure (SDS p = 0.11 and p = 0.37, respectively) in Glut1D children treated with KDT for at least 10 years compared to healthy controls.

CONCLUSIONS

In contrast to previous short-term reports on adverse effects of KDT, 10-year follow-up did not identify cardiovascular risks of dietary treatment for Glut1D.

Genetic Identification in Early Onset Parkinsonism among Norwegian Patients

BACKGROUND

An initial diagnosis of Parkinson's disease (PD) is challenging, especially in patients who have early onset and atypical disease. A genetic etiology for parkinsonism, when established, ends that diagnostic odyssey and may inform prognosis and therapy. The objective of this study was to elucidate the genetic etiology of parkinsonism in patients with early onset disease (age at onset <45 years).

METHODS

Whole-exome sequencing, copy number variability, and short tandem repeat analyses were performed. The analyses were focused on genes previously implicated in parkinsonism and dystonia in patients with early onset parkinsonism. Genotype-phenotype correlations were assessed using regression models.

RESULTS

The patient cohort was characterized by early onset, slowly progressive parkinsonism with a mean age at onset of 39.2 ± 5.0 years (n = 108). By 10 years of disease duration, the mean Hoehn & Yahr stage was 2.6 ± 0.8, the mean Unified Parkinson's Disease Rating Scale, part III (motor part) score was 24.9 ± 12.1 (n = 83), and 30 patients were cognitively impaired at the last examination (Montreal Cognitive Assessment score ≤ 26). Ten patients with typical early onset PD harbored homozygous or compound heterozygous mutations phosphatase and tensin homolog-induced putative kinase 1 (PINK1) (n = 4), parkin (PRKN) (n = 3), or the leucine-rich repeat kinase 2 (LRRK2) c.6055 G to A transition (n = 3). In addition, 5 patients with more atypical disease were compound heterozygotes for the glucocerebrosidase gene (GBA) (n = 3) 1 was heterozygous for solute carrier family 2, member 1 (SLC2A1) and another carried a novel ataxin 2 (ATXN2) exon 1 duplication. In most patients, the cumulative mutational burden did not appear to contribute to age at onset or progression.

CONCLUSION

In this clinical series, 15 patients (14%) carried mutations that were linked to monogenic parkinsonism. GBA carriers were most likely to suffer an earlier cognitive demise. Nevertheless, the etiology for most patients with early onset PD remains to be determined.

GLUT1-deficiency syndrome: Report of a four-generation Norwegian family with a mild phenotype

INTRODUCTION

Glucose transporter type 1 deficiency syndrome (GLUT1-DS) is a rare metabolic encephalopathy with a wide variation of clinical phenotypes. Familial variants are often milder than de novo cases, and may therefore remain undiagnosed. The aim of this study was to characterize the clinical course of GLUT1-DS in a four-generation Norwegian family where the oldest generations had never received any treatment.

METHOD

Through interviews and clinical investigations, we characterized a family of 26 members, where 11 members had symptoms strongly suggesting GLUT1-DS. All members were offered genetic testing of the SLC2A1 gene. Affected members were offered treatment with ketogenic diet, and the effect of the treatment was registered.

RESULTS

We sequenced the SLC2A1 gene in 13 members, and found that 10, all with symptoms, had the c.823G>A (p.Ala275Thr) variant. All affected members had experienced early-onset epilepsy, paroxysmal exercise-induced dyskinesias, and most had mild learning disability. Moreover, some had symptoms and signs of a distal neuropathy in addition to reduced sense of orientation and excessive daytime sleep. Their load of symptoms had decreased over the years, although that they never had received any treatment. Nevertheless, those who started dietary treatment all experienced an improved quality of life.

CONCLUSION

We report a four-generation family with GLUT1-DS where the disease has a mild course, even when untreated. In addition to classical GLUT1-DS features, we also describe symptoms which have never been reported in GLUT1-DS previously. As such, this family extends the phenotypic spectrum of GLUT1-DS and underlines the importance of diagnosing also relatively mildly affected patients, even in adult life, as they also seem to benefit from dietary treatment.

Novel mutation in a patient with late onset GLUT1 deficiency syndrome

Glucose transporter 1 deficiency syndrome (GLUT1-DS) is an inborn error of metabolism caused by impaired glucose transport through blood brain barrier due to mutation in SLC2A1 gene, encoding transporter protein. Clinical spectrum includes various signs and symptoms, ranging from severe epileptic encephalopathy to movement disorders. The diagnosis of GLUT1-DS requires hypoglycorrhachia in the presence of normoglycaemia with a reduced cerebrospinal fluid (CSF):plasma glucose ratio. The absence of pathogenic mutation in SLC2A1 gene does not exclude the diagnosis. This case report describes a patient with late onset GLUT1-DS with a novel sporadic mutation c.539T>A, p.Met180Lys in exon 5 of the SLC2A1 gene. The dominating clinical features were epilepsy and paroxysmal dyskinesias provoked by infection, emotional stress and fasting. The ictal EEG was characterized by generalized paroxysmal 3-3.5Hz spike-slow wave complexes (absences). Treatment with ketogenic diet showed clinical improvement with the reduction of paroxysmal dyskinesias.

Paroxysmal eye-head movements in Glut1 deficiency syndrome

Objective:

To describe a characteristic paroxysmal eye–head movement disorder that occurs in infants with Glut1 deficiency syndrome (Glut1 DS).

Methods:

We retrospectively reviewed the medical charts of 101 patients with Glut1 DS to obtain clinical data about episodic abnormal eye movements and analyzed video recordings of 18 eye movement episodes from 10 patients.

Results:

A documented history of paroxysmal abnormal eye movements was found in 32/101 patients (32%), and a detailed description was available in 18 patients, presented here. Episodes started before age 6 months in 15/18 patients (83%), and preceded the onset of seizures in 10/16 patients (63%) who experienced both types of episodes. Eye movement episodes resolved, with or without treatment, by 6 years of age in 7/8 patients with documented long-term course. Episodes were brief (usually <5 minutes). Video analysis revealed that the eye movements were rapid, multidirectional, and often accompanied by a head movement in the same direction. Eye movements were separated by clear intervals of fixation, usually ranging from 200 to 800 ms. The movements were consistent with eye–head gaze saccades. These movements can be distinguished from opsoclonus by the presence of a clear intermovement fixation interval and the association of a same-direction head movement.

Conclusions:

Paroxysmal eye–head movements, for which we suggest the term aberrant gaze saccades, are an early symptom of Glut1 DS in infancy. Recognition of the episodes will facilitate prompt diagnosis of this treatable neurodevelopmental disorder.

Analysis of Gait Disturbance in Glut 1 Deficiency Syndrome

Anticipating potential therapies for Glut 1 deficiency syndrome (Glut1DS) emphasizes the need for effective clinical outcome measures. The 6-minute walk test is a well-established outcome measure that evaluates walking ability in neurological diseases. Twenty-one children with Glut 1 deficiency syndrome and 21 controls performed the 6-minute walk test. Fatigue was determined by comparing distance walked in the first and sixth minutes. Gait was analyzed by stride length, velocity, cadence, base of support, and percentage time in double support. Independent sample t-tests examined differences between group. Repeated-measures analysis of variance evaluated gait parameters over time. Glut 1 deficiency syndrome patients walked less (P < .05), had slower velocities (P < .0001), had shorter stride lengths (P < .0001), spent more time in double support (P < .001), and had increasing variability in base of support (P = .009). Glut 1 deficiency syndrome patients have impaired motor performance, walk more slowly, and have poor balance. The 6-minute walk test with gait analysis may serve as a useful outcome measure in clinical trials in Glut 1 deficiency syndrome.

A 23 years follow-up study identifies GLUT1 deficiency syndrome initially diagnosed as complicated hereditary spastic paraplegia

Glucose transporter 1 (GLUT1) deficiency syndrome (GLUT1DS) was initially described in the early 90s as a sporadic clinical condition, characterized by seizures, motor and intellectual impairment with variable clinical presentation, and without a known genetic cause. Although causative mutations in SLC2A1 were later identified and much more is known about the disease, it still remains largely underdiagnosed. In the current study, a previously described Italian family was re-analyzed using whole exome sequencing and clinically re-evaluated. Affected individuals presented with spastic paraplegia as a predominant symptom, with epilepsy and intellectual disability, inherited as an autosomal dominant trait with variable clinical presentation. While a novel variant of hereditary spastic paraplegia (HSP) was initially hypothesized in this family, previous linkage studies of known HSP genes did not identify the genetic cause. Exome-sequencing study identified a p.Arg126Cys mutation in the SLC2A1 gene, encoding GLUT1, which segregated with the affected members of the family. The diagnosis of GLUT1DS was further confirmed by cerebrospinal fluid analysis, and treatment was started with good initial response. The description of this large family provides further clinical information on this rare disease. It also offers an example of how GLUT1DS can be challenging to diagnose, and emphasizes the importance of lumbar puncture in the workflow of similar syndromes. Finally, it suggests that analysis of SLC2A1 should be considered in the diagnostic work up of HSP, especially if it is associated with epilepsy.

Atypical Manifestations in Glut1 Deficiency Syndrome

Glucose transporter type 1 deficiency syndrome is a genetically determined, treatable, neurologic disorder that is caused by an insufficient transport of glucose into the brain. It is caused by a mutation in the SCL2A1 gene, which is so far the only known to be associated with this condition. Glucose transporter type 1 deficiency syndrome consists of a wide clinical spectrum that usually presents with cognitive impairment, epilepsy, paroxysmal exercise-induced dyskinesia, acquired microcephaly, hemolytic anemia, gait disturbance, and dyspraxia in different combinations. However, there are other clinical manifestations that we consider equally peculiar but that have so far been poorly described in literature. In this review, supported by a video contribution, we will accurately describe this type of clinical manifestation such as oculogyric crises, weakness, paroxysmal kinesigenic and nonkinesigenic dyskinesia in order to provide an additional instrument for a correct, rapid diagnosis.

Diagnosing Glucose Transporter 1 Deficiency at Initial Presentation Facilitates Early Treatment

OBJECTIVE

To profile the initial clinical events of glucose transporter 1 deficiency syndrome (Glut1 DS) in order to facilitate the earliest possible diagnosis.

STUDY DESIGN

We retrospectively reviewed 133 patients with Glut1 DS from a single institution. Family interviews and medical record reviews identified the first clinical event(s) reported by the caregivers.

RESULTS

Average age of the first event was 8.15 ± 11.9 months (range: 0.01-81). Ninety-one patients experienced the first symptom before age 6 months (68%). Thirty-three additional patients (25%) presented before age 2 years. Only 9 patients (7%), reported the first event after age 2 years. Seizures were the most common first event (n = 81, 61%), followed by eye movement abnormalities (n = 51, 38%) and changes in muscle strength and tone (n = 30, 22%). Eye movement abnormalities, lower cerebrospinal fluid glucose values, and lower Columbia Neurological Scores correlated with earlier onset of the first event (r: -0.17, 0.22, and 0.25 respectively, P < .05). There was no correlation with age of first event and red blood cell glucose uptake or mutation type.

CONCLUSIONS

Glut1 DS is a treatable cause of infantile onset encephalopathy. Health care providers should recognize the wide spectrum of paroxysmal events that herald the clinical onset of Glut1 DS in early infancy to facilitate prompt diagnosis, immediate treatment, and improved long-term outcome.

CoQ10 Deficiency Is Not a Common Finding in GLUT1 Deficiency Syndrome

CoQ₁₀ deficiency has been recently described in tissues of a patient with GLUT1 deficiency syndrome. Here, we investigated patients and mice with GLUT1 deficiency in order to determine whether low CoQ is a recurrent biochemical feature of this disorder, to justify CoQ₁₀ supplementation as therapeutic option.CoQ₁₀ levels were investigated in plasma, white blood cells, and skin fibroblasts of 16 patients and healthy controls and in the brain, cerebellum, liver, kidney, muscle, and plasma of 4-month-old GLUT1 mutant and control mice.CoQ₁₀ levels in plasma did not show any difference compared with controls. Since most of the patients studied were on a ketogenic diet, which can alter CoQ₁₀ content in plasma, we also analyzed white blood cells and cultured skin fibroblasts. Again, we found no differences. In mice, we found slightly reduced CoQ in the cerebellum, likely an epiphenomenon, and activity of the mitochondrial respiratory chain enzymes was normal.Our data from GLUT1 deficiency patients and from GLUT1 model mice fail to support CoQ₁₀ deficiency as a common finding in GLUT1 deficiency, suggesting that CoQ deficiency is not a direct biochemical consequence of defective glucose transport caused by molecular defects in the SLC2A1 gene.

The role of SLC2A1 mutations in myoclonic astatic epilepsy and absence epilepsy, and the estimated frequency of GLUT1 deficiency syndrome

The first mutations identified in SLC2A1, encoding the glucose transporter type 1 (GLUT1) protein of the blood-brain barrier, were associated with severe epileptic encephalopathy. Recently, dominant SLC2A1 mutations were found in rare autosomal dominant families with various forms of epilepsy including early onset absence epilepsy (EOAE), myoclonic astatic epilepsy (MAE), and genetic generalized epilepsy (GGE). Our study aimed to investigate the possible role of SLC2A1 in various forms of epilepsy including MAE and absence epilepsy with early onset. We also aimed to estimate the frequency of GLUT1 deficiency syndrome in the Danish population. One hundred twenty patients with MAE, 50 patients with absence epilepsy, and 37 patients with unselected epilepsies, intellectual disability (ID), and/or various movement disorders were screened for mutations in SLC2A1. Mutations in SLC2A1 were detected in 5 (10%) of 50 patients with absence epilepsy, and in one (2.7%) of 37 patient with unselected epilepsies, ID, and/or various movement disorders. None of the 120 MAE patients harbored SLC2A1 mutations. We estimated the frequency of SLC2A1 mutations in the Danish population to be approximately 1:83,000. Our study confirmed the role of SLC2A1 mutations in absence epilepsy with early onset. However, our study failed to support the notion that SLC2A1 aberrations are a cause of MAE without associated features such as movement disorders.

From splitting GLUT1 deficiency syndromes to overlapping phenotypes

INTRODUCTION

Glucose transporter type 1 deficiency syndrome (GLUT1DS) is a rare genetic disorder due to mutations or deletions in SLC2A1, resulting in impaired glucose uptake through the blood brain barrier. The classic phenotype includes pharmacoresistant epilepsy, intellectual deficiency, microcephaly and complex movement disorders, with hypoglycorrhachia, but milder phenotypes have been described (carbohydrate-responsive phenotype, dystonia and ataxia without epilepsy, paroxysmal exertion-induced dystonia). The aim of our study was to provide a comprehensive overview of GLUT1DS in a French cohort.

METHODS

265 patients were referred to the French national laboratory for molecular screening between July 2006 and January 2012. Mutations in SLC2A1 were detected in 58 patients, with detailed clinical data available in 24, including clinical features with a focus on their epileptic pattern and electroencephalographic findings, biochemical findings and neuroimaging findings.

RESULTS

53 point mutations and 5 deletions in SLC2A1 were identified. Most patients (87.5%) exhibited classic phenotype with intellectual deficiency (41.7%), epilepsy (75%) or movement disorder (29%) as initial symptoms at a medium age of 7.5 months, but diagnostic was delayed in most cases (median age at diagnostic 8 years 5 months). Sensitivity to fasting or exertion in combination with those 3 main symptoms were the main differences between mutated and negative patients (p < 0.001). Patients with myoclonic seizures (52%) evolved with more severe intellectual deficiency and movement disorders compared with those with Early Onset Absence Epilepsy (38%). Three patients evolved from a classic phenotype during early childhood to a movement disorder predominant phenotype at a late childhood/adulthood.

CONCLUSIONS

Our data confirm that the classic phenotype is the most frequent in GLUT1DS. Myoclonic seizures are a distinctive feature of severe forms. However a great variability among patients and overlapping through life from milder classic phenotype to paroxysmal-prominent- movement-disorder phenotype are possible, thus making it difficult to identify definite genotype-phenotype correlations.

Paroxysmal movement disorders

Paroxysmal dyskinesias represent a group of episodic abnormal involuntary movements manifested by recurrent attacks of dystonia, chorea, athetosis, or a combination of these disorders. Paroxysmal kinesigenic dyskinesia, paroxysmal nonkinesigenic dyskinesia, paroxysmal exertion-induced dyskinesia, and paroxysmal hypnogenic dyskinesia are distinguished clinically by precipitating factors, duration and frequency of attacks, and response to medication. Primary paroxysmal dyskinesias are usually autosomal dominant genetic conditions. Secondary paroxysmal dyskinesias can be the symptoms of different neurologic and medical disorders. This review summarizes the updates on etiology, pathophysiology, genetics, clinical presentation, differential diagnosis, and treatment of paroxysmal dyskinesias and other episodic movement disorders.

Treatment of paroxysmal dyskinesias in children

OPINION STATEMENT

Paroxysmal dyskinesia represents a group of uncommon movement disorders that are characterized by episodes of abnormal movements arising from a baseline of normal or nearly normal movement. Recent advances in the genetics of these disorders have helped provide some unification of classification schemes and better understanding. However, the approach to treatment continues to be based on the phenotype more than the genotype. The treatment approach is primarily based on the factors that precipitate the episodes of abnormal movements. For paroxysmal kinesigenic dyskinesia (PKD) in which the spells are triggered by sudden movement, treatment with anticonvulsants that target voltage-sensitive sodium channels (e.g., carbamazepine or phenytoin) is highly effective. For paroxysmal nonkinesigenic dyskinesia (PNKD), treatment with benzodiazepines is effective in many patients. PNKD episodes are often precipitated by caffeine, ethanol, or sleep deprivation, and lifestyle modifications are often helpful. Paroxysmal exertion-induced dyskinesia (PED) is less likely to respond to medications, but the ketogenic diet or modified Atkins diet may provide benefit. As more knowledge is gained about the underlying biology of these disorders, additional treatments may emerge.