Pyridoxal phosphate-responsive seizures

Pyridoxal phosphate-responsive seizures (sometimes called pyridoxamine 5'-phosphate oxidase deficiency or PNPO deficiency) is a condition in which repeated seizures (epilepsy) typically begin within the first two weeks of life. In approximately 10 percent of individuals with PNPO deficiency, the seizures have a later onset, beginning after the first month of life. The seizures typically involve irregular involuntary muscle contractions (myoclonus), abnormal eye movements, or convulsions. In some cases, the seizures may last for several minutes or the seizures may occur too close together to allow for recovery between episodes (status epilepticus). Some babies with PNPO deficiency will experience seizures before birth, and some will experience a slow heart rate and a lack of oxygen before delivery (fetal distress).

Anticonvulsant medications, which are usually given to control seizures, are not effective in people with PNPO deficiency. Instead, individuals with PNPO deficiency require lifelong treatment with one of the following forms of vitamin B6: pyridoxal 5'-phosphate (PLP) or pyridoxine. If untreated, people with this condition can develop severe brain dysfunction (encephalopathy), which can lead to death. Even though seizures can be controlled with PLP or pyridoxine, people with PNPO deficiency may still experience neurological problems such as developmental delays, learning disorders, and uncontrolled movements (dystonia).

Other conditions present with signs and symptoms that are very similar to those seen in people with PNPO deficiency. These include pyridoxine-dependent epilepsy caused by changes in the ALDH7A1 gene and PLPBP deficiency caused by changes in the PLPBP gene. Individuals with these conditions are also typically treated with a form of vitamin B6.