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.