Novel SPTBN1 Nonsense Variant Presenting as Apparent Autoimmune Encephalitis: A Diagnostic Lesson in New-Onset Refractory Seizures

New-onset refractory seizures in children with pre-existing neurodevelopmental disorders present a diagnostic challenge. We report a child with a history of multiple developmental disorders found to have a novel pathogenic SPTBN1 nonsense variant who presented with new-onset refractory seizures fulfilling criteria for probable antibody-negative autoimmune encephalitis (AE), improved with immunotherapy, and was ultimately diagnosed with a genetic epilepsy. Her brother carries the identical variant and has a similar developmental phenotype except that he has never had seizures, demonstrating intrafamilial variable expressivity.