Hyperpipecolic acidemia: clinical, biochemical, and radiologic observations

Fetal onset ventriculomegaly and subependymal cysts in a pyridoxine dependent epilepsy patient

Pyridoxine dependent epilepsy (PDE) is caused by mutations in the ALDH7A1 gene encoding α-aminoadipic semialdehyde dehydrogenase. The classic clinical presentation is neonatal seizures responsive only to pyridoxine therapy. White matter abnormalities, corpus callosum agenesis or hypoplasia, megacisterna magna, cortical dysplasia, neuronal heterotopias, intracerebral hemorrhage, and hydrocephalus in neuroimaging have been reported in patients with PDE. We report a new patient with asymmetric progressive ventriculomegaly noted on fetal sonography at 22 weeks' gestation. Postnatal brain sonography on day 1 and MRI on day 5 confirmed bilateral asymmetric ventriculomegaly caused by bilateral subependymal cysts. Intractable seizures at age 7 days initially responded to phenobarbital. Markedly elevated urinary α-aminoadipic acid semialdehyde levels and compound heterozygous mutations in the ALDH7A1 gene (c.446C>A/c.919C>T) confirmed the diagnosis of PDE caused by ALDH7A1 genetic defect. Despite the presence of structural brain malformations and subependymal cysts, PDE should always be included in the differential diagnosis of neonatal seizures that are refractory to treatment with antiepileptic drugs.

New Amperometric Biosensors Based on Diamond Paste for the Assay ofL‐ andD‐Pipecolic Acids in Serum Samples

Monocrystalline natural diamond, L-amino acid oxidase (L-AAOD), D-amino acid oxidase (D-AAOD), and paraffin oil were used for the design of the modified diamond paste. The technique used for the direct voltammetric assay was differential pulse voltammetry (DPV) with applied potential pulse amplitude of 25 mV vs. Ag/AgCl. Using the new amperometric biosensors L-pipecolic acid (L-PA) and D-pipecolic acid (D-PA) were determined reliably from serum samples at 700 and 200 mV vs. Ag/AgCl, respectively, with low limits of detection.

Determination of l-Pipecolic Acid in Plasma Using Chiral Liquid Chromatography-Electrospray Tandem Mass Spectrometry

Background: l-Pipecolic acid (L-PA), an important biochemical marker for the diagnosis of peroxisomal disorders, is usually determined as the racemate. We developed a chiral liquid chromatography-tandem mass spectrometry (LC-MS/MS) method for the analysis of L-PA in plasma.

Methods: We used a narrow bore chiral macrocyclic glycopeptide teicoplanin column for the enantioseparation of d-pipecolic acid (D-PA) and L-PA and interfaced the column directly to the electrospray source of a tandem mass spectrometer. We used phenylalanine-d5 as internal standard added to 50 μL of plasma followed by deproteinization, evaporation, and injection. The analysis was performed in the selected-reaction monitoring mode using two transitions: m/z 130→m/z 84 for PA, and m/z 171→m/z 125 for phenylalanine-d5. L-PA eluted at 7 min, and D-PA eluted at 11.7 min, whereas phenylalanine-d5 eluted at 6 min. The turnaround time for the assay was 20 min.

Results: Linear calibration curves were obtained in the range of 0.5–80 μmol/L. At a plasma concentration of 1.0 μmol/L, the signal-to-noise ratio was 50:1. The intra- and interassay variations were 3.1–7.9% and 5.7–13%, respectively, at concentrations of 1–50 μmol/L. Mean recoveries of L-PA added to plasma were 95% (5 μmol/L) and 102% (50 μmol/L). The method clearly distinguished between healthy individuals and peroxisomal disease patients.

Conclusions: The novel LC-MS/MS method is simple, rapid, and stereoselective, and uses only 50 μL of plasma, no derivatizing reagents, and a commercially available internal standard. Sample preparation is not complex and is faster than for all other methods.