Atypical vitamin B6 deficiency: a rare cause of unexplained neonatal and infantile epilepsies.

ALDH7A1 and PNPO deficiencies are rare inborn errors of vitamin B6 metabolism causing perinatal seizure disorders. The phenotypic variability, however, is broad. To assess the frequency of these deficiencies in unexplained infantile epilepsy, we screened 113 patients for mutations in both genes. We identified 1 patient with an epilepsy phenotype resembling Dravet syndrome and likely pathogenic mutations in ALDH7A1. Presenting features were highly atypical of pyridoxine-dependent epilepsy, including febrile seizures, response to anticonvulsive drugs, and periods of seizure freedom without pyridoxine treatment. "Hidden" vitamin B6 deficiencies might be rare but treatable causes of unexplained epilepsy extending beyond the classical phenotypes.