ALDH7A1 and pyridoxine-dependent epilepsy: In 3 out of 6 patients (50%), the diagnosis was suspected based on the abnormal CSF HVA and/or 5-HIAA levels leading to diagnosis of the following inherited neurotransmitter disorders including autosomal dominant GTPCH deficiency, TH deficiency, pyridoxine dependent epilepsy (PDE) caused by mutations in the ALDH7A1 gene (PDE-ALDH7A1) (Table 2).