Glucose transporter type 1 deficiency syndrome (GLUT1-DS) – delayed diagnosis and treatment. A case report

Abstract

Background. Glucose transporter type 1 deficiency syndrome (GLUT1-DS) is a treatable metabolic disorder caused by mutation in the SLC2A1 gene. The functional deficiency of the GLUT1 protein leads to impaired glucose transport into the brain, resulting in a spectrum of neurological phenotypes. The most severe classic phenotype comprises infantile-onset epileptic encephalopathy associated with delayed development, acquired microcephaly, motor coordination disturbances, and spasticity. The less severe clinical features, such as paroxysmal exercise-induced dystonia with or without epileptic seizures, are also observed. Aim. Hypothesis, that one possible treatment option entails intrathecal injection of glucose. Material and Methods. We describe a woman, who was diagnosed as having epilepsy and treated for years with different antiepileptic drugs with no clinical effect. She had only two generalized tonic clonic seizures in her life. The patient suffered from increasing frequency of the paroxysmal involuntary movements of lower limbs, leading to gait disturbances and falls, which were misdiagnosed as epileptic seizures. The jerks of the head and limbs were observed from the first months of her life. The symptoms were provoked by stress and exertion. Additionally, mild intellectual disability was noted during her growth. Results. Glucose concentrations in cerebrospinal fluid were low. The SLC2A1 gene analysis resulted in the identification of a heterozygous missense mutation p.Arg333Trp. identification. The diagnosis of GLUT1-DS was confirmed. Conclusion. Delayed diagnosis resulted in many problems with the acceptance of the ketogenic diet, which is considered the treatment of choice in GLUT1 deficiency syndromes. To our knowledge, this is the first case report of GLUT1-DS diagnosis occurring in adulthood and published in Poland. Key words: GLUT-1 deficiency • ketogenic diet • epilepsy • dystonia BACKGROUND Glucose is the major carbon and energy source of nerve cells, supporting brain growth and neural excitation. The glucose transporter of capillary endothelial cells located at the blood brain barrier (BBB), facilitates the passive flux of glucose from blood to brain (Wong et al., 2007) and is also responsible for astrocyte glucose