Early-onset cobalamin C/D deficiency: epilepsy and electroencephalographic features.

Purpose: To describe epilepsy and EEG findings in the early-onset cobalamin (Cbl) C/D deficiency, an inborn error of intracellular Cbl metabolism characterized by high plasma levels of methylmalonic acid, homocystine, and homocysteine.

Methods: Type and frequency of seizures were studied in 10 patients (six boys and four girls) who underwent waking and sleep EEG.

Results: Half of patients had seizures in the first year of life (either concurrent with the other symptoms of disease or some months after the onset of disease); seizures occurred after 2 years in the other half of patients.