<h4>Background</h4>Biallelic BRCA1-associated ataxia telangiectasia mutated activator 1 (<i>BRAT1</i>) gene mutations can result in lethal neonatal rigidity and multifocal seizure syndrome (RMFSL), characterized by refractory epilepsy, hypertonia, autonomic dysfunction, and early death. The gene discussed is BRAT1; the disease is neonatal-onset encephalopathy with rigidity and seizures.