Behulova D 1 , Bzduch V 2 , Fabriciova K 2 , Sykora P 3 , Kolnikova M 3 , Syrova D 1 1 Dept Lab Med, Univ Child Hosp, Bratislava, Slovakia 2 1st Dept Pediatr, Univ Child Hosp, Bratislava, Slovakia 3 Dept Child Neurol, Univ Child Hosp, Bratislava, Slovakia Background: Glucose transporter 1-deficiency syndrome (GLUT1-DS) is a cause of the reduced glucose entry into the brain. Our aim was to compare biochemical findings, clinical features and genotypes in patients detected in Slovakia. Methods: Serum (S) glucose, cerebrospinal fluid (CSF) glucose (reference range, RR 2.5-3.9 mmol/l) and lactate (RR 0.70-2.10 mmol/l) were investigated and ratio CSF:S glucose (RR>0.65) was calculated in patients with various neurological and psychiatric symptoms. Genomic DNA for mutation analysis was obtained from blood samples. Results: Now, patients are at the age 7(M), 7(F), 8(F), 9(M) years, their initial biochemical findings were: CSF glucose 1.1, 1.7, 1.8, 2.2 mmol/l; CSF:S glucose ratio 0.19, 0.37, 0.40, 0.48; CSF lactate 0.82, 0.93, 1.30, 1.20 mmol/l and the first clinical symptoms appeared at 2.5, 8, 9 and 48 months respectively. Patient (Pt)1 presented with infantile epilepsy, developmental delay, Pt 2 with apathy, ataxy, Pt 3 with seizures, ataxy, Pt 4 with concentration disorders. Pathogenic mutations c.798_799insC, c.505_507del, c.1119delG were identified in Pt 1, 2, 3 respectively, analysis in SLC2A1 gene is being performed in Pt 4.