Clinical and Genetic Characteristics of Chinese Children With GLUT1 Deficiency Syndrome: Case Report and Literature Review

Objective: GLUT1 deficiency syndrome (GLUT1-DS) is a rare, treatable neurometabolic disorder. However, its diagnosis may be challenging due to the various and evolving phenotypes. Here we report the first Chinese familial cases with genetically confirmed GLUT1-DS and analyze the characteristics of Chinese children with GLUT1-DS from clinical, laboratory, and genetic aspects.Methods: We reported a Chinese family with three members affected with GLUT1-DS and searched for relevant articles up to September 2020 from PubMed, WOS, CNKI, and WanFang databases. A total of 30 Chinese patients diagnosed with GLUT1-DS (three newly identified patients in one family and 27 previously reported ones) were included and analyzed in this study.Results: The median age of onset of the 30 patients (male: 18, female: 12) was 8.5 months (range, 33 days to 10 years). Epileptic seizures were found in 25 patients, most with generalized tonic–clonic and focal ones. Movement disorders were found in 20 patients—frequently with ataxia and dystonia, developmental delay in 25 patients, and microcephaly only in six patients. The cerebrospinal fluid (CSF) analysis showed decreased CSF glucose (median: 1.63 mmol/L, range: 1.1–2.6 mmol/L) and glucose ratio of CSF to blood (median: 0.340; range: 0.215–0.484). The genetic testing performed in 28 patients revealed 27 cases with pathogenic variations of the SLC2A1 gene, including 10 missense, nine frameshift, three nonsense, three large fragment deletions, and two splice-site mutations. Most patients had a good response to the treatment of ketogenic diet or regular diet with increased frequency. Although three patients in this Chinese family carried the same pathogenic mutation c.73C > T (p.Q25X) in the SLC2A1 gene, their symptoms and responses to treatment were not exactly the same.Conclusion: The clinical manifestations of GLUT1-DS are heterogeneous, even among family members sharing the same mutation. For children with unexplained epileptic seizures, developmental delay, and complex movement disorders, detection of low CSF glucose or SLC2A1 gene mutations is helpful for the diagnosis of GLUT1-DS. Early initiation of ketogenic diet treatment significantly improves the symptoms and prognosis of GLUT1-DS.

Polymorphism in the HaeIII single nucleotide polymorphism of the SLC2A1 gene and cardiovascular disease in the early type 2 diabetes mellitus

Introduction: SLC2A1 polymorphism may play a role in the smooth muscle cell proliferation and extracellular matrix synthesis in vessels. However, the role of SLC2A1 polymorphism on diabetic cardiovascular disease (CVD) have not yet been identified. In this study, we aimed to investigate the association between SLC2A1 HaeIII polymorphism and CVD in Korean patients with type 2 diabetes mellitus (T2DM) according to disease duration. Methods: A total of 846 patients with T2DM who visited the Chungbuk National University Hospital were investigated. The HaeIII polymorphism of SLC2A1 gene was determined by real time polymerase chain reaction method. Genotyping results were presented GG, AG, or AA. Subgroup analysis was performed according to duration of T2DM (⩽10, 11–20, >20 years). Results: The AA genotype was significantly associated with higher prevalence of CVD in patients with DM duration less than 10 years (26.3% vs 9.2%, p = 0.014). There was no significant association between SLC2A1 HaeIII polymorphism and other diabetic complications including, retinopathy, nephropathy, neuropathy, cerebrovascular disease, and peripheral artery disease. Conclusions: The SLC2A1 HaeIII polymorphism was associated with CVD in Korean patients with T2DM with short disease duration.

GLUT1 Deficiency Syndrome—Early Treatment Maintains Cognitive Development? (Literature Review and Case Report)

Glucose transporter type 1 (GLUT1) is the most important energy carrier of the brain across the blood–brain barrier, and a genetic defect of GLUT1 is known as GLUT1 deficiency syndrome (GLUT1DS). It is characterized by early infantile seizures, developmental delay, microcephaly, ataxia, and various paroxysmal neurological phenomena. In most cases, GLUT1DS is caused by heterozygous single-nucleotide variants (SNVs) in the SLC2A1 gene that provoke complete or severe impairment of the functionality and/or expression of GLUT1 in the brain. Despite the rarity of these diseases, GLUT1DS is of high clinical interest since a very effective therapy, the ketogenic diet, can improve or reverse symptoms, especially if it is started as early as possible. We present a clinical phenotype, biochemical analysis, electroencephalographic and neuropsychological features of an 11-month-old boy with myoclonic seizures, hypogammaglobulinemia, and mildly impaired gross motor development. Using sequence analysis and deletion/duplication testing, deletion of an entire coding sequence in the SLC2A1 gene was detected. Early introduction of a modified Atkins diet maintained a seizure-free period without antiseizure medications and normal cognitive development in the follow-up period. Our report summarizes the clinical features of GLUT1 syndromes and discusses the importance of early identification and molecular confirmation of GLUT1DS as a treatable metabolic disorder.

SLC2A1 and Its Related Epileptic Phenotypes

Glucose transporter type 1 deficiency syndrome (GLUT1DS) is caused by heterozygous, mostly de novo, mutations in SLC2A1 gene encoding the glucose transporter GLUT1, the most relevant energy transporter in the blood–brain barrier. GLUT1DS includes a broad spectrum of neurologic disturbances, from severe encephalopathy with developmental delay, to epilepsy, movement disorders, acquired microcephaly and atypical mild forms. For diagnosis, lumbar puncture and genetic analysis are necessary and complementary; an immediate response to ketogenic diet supports the diagnosis in case of high suspicion of disease and negative exams. The ketogenic diet is the first-line treatment and should be established at the initial stages of disease.

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.

Glucose Transporter 1 deficiency and associated conditions in children

The article reviews literature devoted to the glucose transporter type I deficiency syndrome (synonyms: GLUT1 deficiency syndrome, de Vivo disease), that is a genetically determined disease caused by pathogenic variants of the SLC2A1 gene. The insufficiency of this protein leads to the disruption of glucose delivery to the brain through the blood-brain barrier. Clinically, the syndrome is manifested by epileptic seizures (mainly as absences or myoclonic seizures), various motor disorders and psychomotor retardation starting from the early age.Early diagnosis (including molecular genetic analysis of the SLC2A1 gene) enables us to start treatment and prevent progression of the symptoms, and to provide the family with genetic consultation on the prognosis and risks for the next generations. Ketogenic diet is an effective treatment option for this pathological condition, it can lead to a regression of the clinical manifestations, especially on the early stage.