Feasibility of newborn screening for pyridoxine-dependent epilepsy.

Background: Pyridoxine-dependent epilepsy (PDE-ALDH7A1) is a developmental epileptic encephalopathy historically characterized by seizures that are resistant to antiseizure medications. Treatment with pyridoxine and lysine reduction therapies are associated with seizure control and improved developmental outcomes. In rare circumstances, patients have died prior to diagnosis and treatment with pyridoxine, and many patients are diagnosed after six months of age when lysine reduction therapies have limited efficacy. Recently two new metabolites were identified (2S,6S-/2S,6R-oxopropylpiperidine-2-carboxylic acid, 2-OPP and 6-oxo-pipecolate, 6-oxo-pip), and we evaluated these metabolites as potential newborn screening biomarkers.

Methods: We recruited participants with a confirmed diagnosis of PDE-ALDH7A1 and retrieved their residual dried blood spots from state-sponsored newborn screening programs. We evaluated the dried blood spots for 2-OPP using commercially available newborn screening kits and equipment, and developed a second-tier test for 6-oxo-pip using LC-MS/MS.

Results: We received eight residual dried blood spots collected before the onset of seizures and the diagnosis of PDE-ALDH7A1. In our newborn screening experiments, 2-OPP was elevated in 7 of 8 samples from affected participants with a mean of 3.08 μmol/L (95 % CI 2.17-3.99) compared to a mean of 0.09 μmol/L (95 % CI 0.09-0.10) in controls (p < 0.001). Second tier testing demonstrated elevated 6-oxo-pip in all samples from affected participants with a mean of 5.66 μmol/L (95 % CI 1.51-9.81) and was undetectable in controls (p < 0.001).

Conclusion: Patients with PDE-ALDH7A1 can be identified using neonatal dried blood spots prior to the onset of symptoms. The use of commercially available newborn screening approaches demonstrates the feasibility of newborn screening for this treatable condition.