Last modified: 2018-09-09
Abstract
Introduction-Glucose transport protein type 1 deficiency syndrome (GLUT1-DS), a chronic brain energy failure prototype resulting in impaired glucose transport in brain, is caused by mutations of the SLC2A1 gene.Three Clinical presentation described are:The classic phenotype, Non-epileptic Glut1-DS and Paroxysmal exercise-induced dyskinesia.CSF glucose <50mg/dl with a normal blood glucose level is highly suggestive.
Case-10 year old boy presented with complaints of progressive episodic gait imbalance , dysarthria since 2 years of age and deteriorating academic performance.Each episodic ataxia lasts for 15 minutes,1 episode per month and progressed to 3-4 episodes per month over 6 months.The child had normal birth history but delayed motor milestones.Neurological examination revealed dull normal intelligence,hyperactive behavior and dysarthric speech. Head circumference, cranial nerve, sensory examination, and reflexes were normal.During the events he had ataxia, choreiform movements of hands. Action tremors, hypotonia , and limb inco-ordination was noted towards the end of an event.MRI brain, EEG and neurometabolic screening were normal.CSF showed low glucose, 38mg/dL with corresponding blood glucose of 86mg/dL.The genetic studies revealed a novel heterozygous 'pathogenic' variant in exon 9 of the SLC2A1 gene.Germline pathogenic variations in the SLC2A1 gene have been shown to be associated with GLUT1 deficiency syndrome. The boy improved with ketogenic diet(KD).
The clinical symptoms although not classic,were suggestive of Glut1-DS(non epileptic variant), which was substantiated by the molecular studies and a novel mutation was identified.
Conclusion-Clinical presentation of GLUT 1DS is varied.It is recommended to consider this diagnosis in cases with unexplained episodic ataxia.