P93 – 2953: Identification of a new mutation of the SCL1A gene in a patient with GLUT1-DS

Objective Diagnostic assessment of a boy of 13 years old. From the age of 16 months, he has showed an isolated oculomotor disorder associated with a delay in acquisition of psychomotor milestones. Furthermore, at 4 years old, he presented absence-like seizures, for whom he has been favourably treated with valproic acid. After 9 years of wellness, when antiepileptic drug was stopped, an effort-related paroxysmal myoclonic dystonia appeared, involving mostly lower limbs. Such episodes have rapidly increased in frequency, becoming truly debilitating for the patient. Methods Suspecting a deficit of the enzyme GLUT1, the patient underwent lumbar puncture, video-EEG and molecular genetic analysis. Physical-chemical analysis of CSF demonstrated a glycorrhachia of 45 mg/dL, lactate at the lower limit of the normal range and a CSF/serum glucose ratio of 0.52. Video-EEG excluded epileptic paroxysms. Results The molecular investigation revealed a point mutation not previously described in literature (c.1199G>A; exon 9 – gene SLC2A1); this mutation was absent in parental alleles and thus it was originated de novo. Conclusion After diagnosis, the patient restarted therapy with valproic acid and began to follow strictly ketogenic diet, getting a complete and persistent clinical remission. In conclusion, this report of a GLUT1-DS case is characterized by an unusual presentation and the description of a new causative mutation. More interestingly, it proves the importance of CSF analysis to potentially reveal treatable diseases in children with undiagnosed movement disorders.