STX1B-related epilepsy in a 24-month-old female infant

We report on a 24-month-old girl with age-appropriate development and normal intellectual ability suffering from myoclonic astatic epilepsy. Panel-based sequencing of roughly 1500 genes associated with neurodevelopmental and metabolic diseases identified a heterozygous de novo point mutation in STX1B (c.733C>T or p.Arg245*). STX1B encodes Syntaxin-1B which plays a role for synaptic transmission. STX1B variants are associated with a broad phenotypic spectrum of epilepsies including febrile or afebrile seizures as well as epileptic encephalopathies. Our patient with MAE adds to the spectrum of STX1B associated phenotypes.