In a 6-year-old girl, born of consanguineous Arab parents from a Bedouin kindred from Qatar, with GLUT1 deficiency syndrome-1, Klepper et al. (2009) identified a homozygous c.1402C>T transition in exon 10 of the SLC2A1 gene, resulting in an arg468-to-trp (R468W) substitution. She was noted to have unsteady ataxic gait at age 18 months, as well as paroxysmal choreoathetosis. She also had developmental delay and hypotonia. EEG showed a polymorphic baseline alpha-theta activity with an isolated monomorphic sharp wave focus. Lumbar puncture showed hypoglycorrhachia and decreased CSF lactate. Her clinically asymptomatic 2-year-old sister was also homozygous for the mutation; she was found to have hypoglycorrhachia and decreased CSF lactate. The parents, who were unaffected, were heterozygous for the mutation. Klepper et al. (2009) concluded that the mutation was pathogenic, since the affected residue is highly conserved, is located in the C terminus which is essential for substrate recognition and transport, and was not found in 120 control alleles. Klepper et al. (2009) suggested that the unaffected sister who was homozygous for the mutation was too young for symptom onset. The findings suggested that GLUT1 deficiency can also be inherited in an autosomal recessive pattern.