Abstracts

Rationale: To evaluate the utility of pyridoxal 5'-phosphate (PLP) levels in the cerebrospinal fluid (CSF) for the diagnosis of antiquitin (ALDH7A1) deficiency, we determined CSF concentrations of PLP, pipecolic acid, and alpha-aminoadipic semialdehyde (a-AASA) in neonates and infants (=12 months of age) with epilepsy. Methods: We prospectively recruited pediatric patients who underwent lumbar puncture to investigate their neurological symptoms, such as epilepsy, developmental retardation, and involuntary movements. This study was approved by the ethics committee of Okayama University. Written informed consent was obtained from all patients or their guardians before the procedure. The collected CSF was protected from light and stored at -80C until analysis. When a CSF sample was collected outside Okayama University Hospital, the sample was shipped on dry ice to our laboratory. After pre-column derivatization of PLP by semicarbazide hydrochloride, we determined the CSF PLP concentration using high-performance liquid chromatography with fluorescent detection (HPLC-FLD). In this study, we only included patients aged =12 months with epilepsy. We excluded those who had already been treated with vitamin B6 (pyridoxine or PLP) at the time of CSF collection. We also measured CSF pipecolic acid and a-AASA using HPLC-FLD in patients with low ( < 14 nmol/L) PLP values. Results: Two hundred and forty-six patients had CSF PLP measured in our laboratory between May 2012 and May 2016. There were 48 patients aged =12 months with epilepsy. Ten patients treated with PLP at the time of CSF collection were excluded. In the remaining 38 patients, four had epileptic seizures that responded to PLP. There were 12 patients with low CSF PLP concentrations, including all four patients with PLP-responsive seizures. In these 12 patients with low CSF PLP levels, CSF pipecolic acid was elevated in three (9.8, 1.8, and 0.7 mol/L), and two of them also had elevated CSF a-AASA (9.4, 8.2 mol/L). Both patients had epileptic seizures that completely resolved with PLP therapy, suggesting a diagnosis of antiquitin deficiency. Seizures in one patient with elevated pipecolic acid (0.7 mol/L) and normal a-AASA ( < 0.1 mol/L) did not respond to PLP therapy. Conclusions: Although the sample size is small, low CSF PLP is frequently observed in vitamin B6-responsive seizures. This lacks specificity for a diagnosis of antiquitin deficiency, however. Other causes, including PNPO deficiency, remain to be clarified for patients with low CSF PLP values with normal pipecolic acid and a-AASA levels. Funding: This work was supported by JSPS KAKENHI Grant Number JP15K09622.