Inherited glycosylphosphatidylinositol deficiency successfully treated with high-dose pyridoxine therapy initiated in adulthood: A case report

Epilepsy is a typical symptom of inherited glycosylphosphatidylinositol deficiency (IGD) that often follows a drug-resistant course. High-dose pyridoxine therapy has been reported to be effective in selected cases of IGD-associated drug-resistant epilepsy. Most reports of effective outcomes describe treatment initiated in childhood, and data on treatment initiation in adulthood remain limited. A 22-year-old woman received high-dose pyridoxine therapy. She was being treated with high-dose phenobarbital (290 mg/day), with a blood concentration of 100 μg/mL, along with four anti-seizure medications, including topiramate, perampanel, zonisamide, and clonazepam. Her seizure frequency fluctuated, and she experienced more than 10 seizures per day, indicating inadequate control. A targeted exome sequencing panel identified compound heterozygous variants in the PIGO gene. Pyridoxine was started at a dose of 15 mg/kg/day and increased to 30 mg/kg/day 2 weeks later. Following the initiation of pyridoxine treatment, the patient experienced no clinical seizures during hospitalization. She exhibited no obvious side effects such as vomiting or liver dysfunction. At 1 year after introduction, the seizure frequency improved to only several times per month. In the present case of refractory epilepsy associated with IGD, high-dose pyridoxine therapy effectively controlled epileptic seizures and was administered without notable adverse events. In recent years, the increased use of genetic testing, including whole-exome sequencing, has led to an increase in early-diagnosed cases. Further data accumulation is necessary to evaluate outcomes in cases diagnosed and treated early in childhood and those diagnosed and treated in adulthood, as in the present case.