ABSTRACT
Glucose transporter type 1 (GLUT1) deficiency is an inborn error of glucose transport. Clinical manifestations are presumed secondary to reduced glucose transport across the blood brain barrier, and include seizures, abnormal tone, developmental delay and hypoglycorrhachia. A high index of suspicion is important as GLUT1 deficiency is a potentially treatable cause of mental retardation. We studied two affected children by continuous video-EEG in order to better understand the cause of the clinical manifestations and improvement on a ketogenic diet. The EEG was characterized by generalized paroxysmal 2-2.5 Hz spike-wave discharges, although normal EEGs were also obtained. Atypical absence seizures were the most prominent clinical seizure. Epileptiform activity and clinical seizures occurred in both children while acutely ketotic and non-ketotic, but were markedly more frequent in one child when non-ketotic. Discharges were not associated with a reduction in substrate for brain metabolism in the blood at that time. Conclusion Atypical absence seizures are common in glucose transporter type 1 deficiency and should alert the clinician to the possibility of this treatable disorder when present in a young child with developmental delay. Our data suggest that the therapeutic mechanism of the ketogenic diet in this disorder is more complicated than simply delivering ketones as an alternative substrate for brain metabolism.
Subject(s)
Monosaccharide Transport Proteins/deficiency , Child , Dietary Fats/administration & dosage , Electroencephalography/methods , Glucose/metabolism , Humans , Intellectual Disability/etiology , Ketosis , Male , Metabolism, Inborn Errors/complications , Metabolism, Inborn Errors/diet therapy , Seizures/diagnosis , Seizures/etiology , Seizures/therapyABSTRACT
UNLABELLED: A new case of mitochondrial malonyl coenzyme A decarboxylase deficiency is described. The patient presented with an initial episode of metabolic acidosis, seizures, hypoglycemia, and cardiac failure at 2 months of age which slowly resolved. Subsequent evaluations at 4 years of age for developmental delay revealed a prominent elevation of malonic acid in urine. Malonyl carnitine was also elevated. The activity of Malonyl CoA decarboxylase in cultured fibroblasts was 7% of normal. CONCLUSION: Malonyl CoA decarboxylase deficiency may result in inhibition of fatty acid oxidation, which may account for the cardiomyopathy.
