Neurodevelopmental Outcome of Early Dietary Lysine Restriction in Pyridoxine Dependent Epilepsy Patients

Inclusion Criteria: * Diagnosis of pyridoxine-dependent epilepsy based on clinical symptoms and elevated levels of plasma or urine AASA. Confirmation by at least one known disease causing mutation in the ALDH7A1 gene to be obtained within one month of enrollment. * Participant is male or female \<3 years of age. * Participants in the test arm have to be less than 3 months of age when the dietary restriction was started. * Participants in the control arm may be older than 3 months of age but must not be older than 3 years of age when they are enrolled into the study and must have been on pyridoxine treatment prior to age 3 months and not treated with dietary lysine restriction at any time during their life. * Participant is managed with a vitamin B6 dose of 15-30 mg/kg/day continuously beginning at \< 3 months age, and willing to maintain this dose for the study duration. * Participants must have been offered dietary lysine restriction as adjunct therapy as part of standard clinical care. * Parent(s) or guardian(s) is willing and able to provide written informed consent after the nature of the study has been explained, and prior to any research-related procedures. Exclusion Criteria: * Diagnosis is not confirmed: Participant does not have a mutation in the ALDH7A1 gene. * Participant was treated prenatally for PDE with pyridoxine (i.e. mother was on pyridoxine) * Timing of dietary restriction: Participant is on a lysine-restricted diet from an age \> 3months. * Confoun…