Pyridoxine-dependent status epilepticus diagnosed during infancy

Abstract

Pyridoxine dependence is a very rare inborn error of metabolism. The disorder develops mainly during the early neonatal period, and cases diagnosed in infants are even rarer. We herein report a case of a 77-day-old boy with status epilepticus diagnosed with pyridoxine dependence. On day 2 after birth, the boy required respiratory management after entering a partial convulsive state. The convulsions did not respond to phenobarbitals and were temporarily controlled by continuous intravenous administration of midazolam. Subsequently, partial seizures occurred frequently, and the patient was observed under treatment with oral phenobarbital and phenytoin, and intravenous midazolam. However, at 65 days of age, partial convulsions of the right upper and lower limbs lasting for one minute occurred episodically in clusters every few to ten minutes. A high dose of phenobarbital was administered and the blood concentration increased to 42 μg/ml, but convulsions were not controlled. At 77 days of age, when 100 mg of pyridoxine was slowly injected intravenously during electroencephalography, the background activity flattened and spikes disappeared. Pyridoxine dependence was diagnosed and all antiepileptic agents were discontinued. Oral administration of pyridoxine at 10 mg/kg/day was started and seizures no longer occurred. Pyridoxine dependence is a treatable inborn error of metabolism. To obtain a diagnosis of pyridoxine dependence, trial administration of pyridoxine is essential, and the pyridoxine test for a definitive diagnosis should also be conducted in cases of status epilepticus during infancy.