Several patients with vitamin-B6 responsive epilepsy but with genetic testing negative for disease-causing variants in ALDH7A1 and PNPO were found to have bi-allelic variants in the PLPBP gene that encodes the proline synthetase co-transcribed homolog (PROSC) which was later renamed as PLP homeostasis protein (PLPHP) (7). The gene discussed is PNPO; the disease is epilepsy.