====== Pyridoxal 5 Phosphate Dependent Epilepsy ======

PNPO deficiency [[https://www.omim.org/entry/603287|(OMIM 6032870)]] is an autosomal recessive inborn error of metabolism that leads to a seizure disorder, presenting in the newborn period (neonatal epileptic encephalopathy) or early infancy, that can be treated with pyridoxal 5’-phosphate but (classically) not pyridoxine. Seizures are often characterized by irregular involuntary muscle contractions (myoclonus), abnormal eye movements, and convulsions.

Mutations in the PNPO gene are responsible for pyridoxal 5'-phosphate-dependent epilepsy. The PNPO gene is responsible for the production of an enzyme called pyridoxine 5'-phosphate oxidase. This enzyme plays a crucial role in metabolizing vitamin B6 from food, specifically pyridoxine and pyridoxamine, into its active form known as pyridoxal 5'-phosphate (PLP). PLP is crucial for various bodily processes, such as protein metabolism and the creation of neurotransmitters that facilitate brain signaling.
===== Classic PNPO deficiency =====

  * defined as neonatal onset in premature infants and neonates
  * Intrauterine seizures, recognized by mothers as episodic, repetitive rhythmic movements
  * Fetal distress before delivery
  * Low APGAR scores
  * Difficult-to-treat seizures irrespective of a history of fetal distress
  * Epileptic encephalopathy or signs of encephalopathy (inconsolable crying, hyperalertness, jitteriness, irritability, dysregulation of muscle tone)
  * Seizures and neurologic findings (e.g., roving eye movements, hypotonia, dystonia) and/or systemic signs (e.g., respiratory distress, anemia, failure to gain weight, abdominal distention, poor feeding)
  * Cryptogenic infantile or epileptic spasms
===== Late-onset PNPO deficiency=====
  * onset after age 28 days in individuals of any age
  * Cryptogenic seizures refractory to common anticonvulsants
==== Standardized Vitamin B6 Trial ====

  * A standardized vitamin B6 trial[(:cite:pmid30671974>{{pmid>long:30671974}})] may raise suspicion regarding PNPO deficiency
  * 40% of individuals with PNPO deficiency are responsive to pyridoxine (PN) and seizures. In a majority of these patients seizures will remit within 1 to 3 days, but it could take upto several days in some cases
  * 60% of individuals with PNPO deficiency who are pyridoxal 5'-phosphate (PLP) responsive, the majority show cessation of seizures in one to three days, accompanied by improvement of abnormal EEG findings.
  * before initiating the vitamin B6 trial:
    * Save plasma and urine; if available, freeze CSF at -80°
    * Resuscitation equipment should be available due to the increased risk of apnea or respiratory arrest with initial dose of either pyridoxine (PN) or pyridoxal 5'-phosphate (PLP)

Steps1
  - Give PN 100mg IV, followed by 30 mg/kg/day IV or p.o. in 2-3 single doses over 1-3 days
  - If PN is ineffective, consider adding folinic acid 3-5 mg/kg/day p.o. in 1-2 single doses
  - If PN & folinic acid are ineffective, replace PN with PLP, 30 to 60 mg/kg/day p.o. in 4-6 single doses over 3 days
If seizures stop: continue pyridoxine or PLP until results of biochemical and/or molecular testing are available

=== How to differentiate pyridoxine or pyridoxal phosphate responsive seizures from other Vitamin B6 responsive seizures ===
  * increased plasma and urinary alpha-aminoadipic semialdehyde is indicative of pyridoxine-dependent epilepsy – //ALDH7A1//
  * increased sulfocysteine is indicative of [[molybdenum cofactor deficiency]] or isolated [[sulfite oxidase deficiency]].
  * there are no biomarkers to differentiate from Pyridoxal 5'-Phosphate-Binding Protein Deficiency (//PLPBP//)( also called PLPHP deficiency). //PLPBP// gene encodes for the protein PLPHP, believed to be crucial for B6 homeostasis

==== References ====