Late-onset drug-resistant epilepsy in pyridoxamine 5'-phosphate oxidase deficiency: a case report

Pyridoxamine 5'-phosphate oxidase deficiency is a rare inborn error of vitamin B₆ metabolism that presents with drug-resistant epileptic seizures. However, the condition is responsive to supplementation with the active vitamin B₆ metabolite pyridoxal 5'-phosphate and, in some cases, pyridoxine.

In this case report, a 10-year-old Iranian male of Fars ethnicity came to a regional hospital in Tehran, Iran with a chief complaint of tic-like movement. He had a history of unintentional, repetitive, and stereotypic movements of both arms since the age of 4 years. The physical examination depicted facial dimorphism. During admission, the patient experienced habitual hypermotor seizures and generalized tonic-clonic seizures. Ictal electroencephalography demonstrated a generalized background attenuation and bursts of generalized, predominantly left-sided, biphasic spike-wave complexes. Whole-genome sequencing revealed a pyridoxamine 5'-phosphate oxidase deficiency as the underlying cause of the drug-resistant seizures, resulting in a low serum level of pyridoxal 5'-phosphate. The patient underwent pyridoxine supplementation therapy, which ultimately resolved his seizures. At 6 months, he was seizure free.

Physicians ought to be aware of manifestations of vitamin B6 deficiency such as mimicking tic and consider it in the differential for drug-resistant epilepsy.