Early onset epileptic encephalopathy with a novel GABRB3 mutation treated effectively with clonazepam

RATIONALE Early onset epileptic encephalopathy (EOEE) is one of the most serious early onset epilepsies. The etiopathology of this condition remains unclear, and recent evidence indicated that gamma-aminobutyric acid (GABA) A receptor, subunit beta 3 (GABRB3) gene mutations might be associated with EOEE. Furthermore, the therapeutic regimen for EOEE has yet to be well elucidated. Herein, we reported the clinical and genetic features of a case with GABRB3-related EOEE. PATIENT CONCERNS A 6-year-old girl developed epileptic seizures 3 days after birth. She presented with multiple seizure types including myoclonic seizures, spasms, and absence seizures. Serial electroencephalographic examinations showed variable abnormalities, and intellectual evaluation revealed significant development retardation. Conventional antiepileptic drugs were ineffective for the seizure controlling. Genetic screening identified a novel nonsense mutation (C.5G > A, p.W2X) in the GABRB3 gene. DIAGNOSES Early onset epileptic encephalopathy. INTERVENTIONS We changed the antiepileptic strategy to oral clonazepam (0.5mg twice daily). The patient was followed up once a week and significant declining in the attack frequency was noted 1 week later (2-3 times daily). Subsequently, the dosage was doubled (1mg twice daily), and complete cessation of seizures was achieved 20 days later. OUTCOMES Through a 9-month follow up,the girl remained seizure-free. LESSONS This study identified a novel nonsensemutation (C.5G>A) in the exon 1 of GABRB3 Gene, which may be associated with EOEE. To our knowledge, this is the first report to use clonazepam in the patient with GABRB3-related EOEE with favorable outcome. Our finding suggested that clonazepam might be a choice for patient with GABRB3-related EOEE. The remarkable efficacy of clonazepam in the control of seizures indicated a potential GABRB3- or GABA-related mechanism involved in the development of EOEE.