GLUT1 deficiency syndrome 2013: current state of the art.

Glucose transporter type 1 deficiency syndrome (GLUT1DS) is the result of impaired glucose transport into the brain. The "classic" GLUT1DS patient presents with infantile seizures (resistant to traditional seizure medications), developmental delay, acquired microcephaly, hypotonia, spasticity, and a complex movement disorder consisting of ataxia and dystonia. However, over the years, other clinical manifestations have been described, such as paroxysmal exertion-induced dystonia with or without seizures, choreoathetosis, alternating hemiplegia, and other paroxysmal events, such as intermittent ataxia, dystonia, and migraine. At the current state of the art in understanding of GLUT1DS, classifying the disease phenotype as "classical" or "non-classical" seems to be of limited clinical utility. It seems more appropriate to think in terms of a broad clinical spectrum in which we can observe intellectual impairment, acquired microcephaly, epilepsy, and movement disorders characterized by different clinical manifestations and degrees of severity. Lumbar puncture, a simple investigation, should be considered the first diagnostic step that, moreover, is feasible worldwide. Thereafter, mutational analysis of the solute carrier family 2 (facilitated glucose transporter) member 1 (SLC2A1) gene should be performed in patients with highly suggestive clinical findings and low cerebrospinal fluid glucose (<50mg/dl or ratio <0.60). Early diagnosis is critical because it allows prompt initiation of treatment with a ketogenic diet (KD). Childhood is the critical period for treatment of GLUT1DS: early diagnosis is crucial for an effective etiological therapy. KD treatment can be useful in adulthood too. Compliance has been found to be much better in GLUT1DS than in the other conditions for which KD treatment is indicated.