Mutations of the syntaxin binding protein 1 (STXBP1) have been associated with 
severe infantile epileptic encephalopathies (Ohtahara syndrome and West 
syndrome), but also with moderate to severe cognitive impairment and 
nonsyndromic epilepsy. We have studied a white infant who presented with focal 
seizures at age 2 weeks. Brain imaging was unremarkable. The 
electroencephalograph (EEG) demonstrated normal background frequency content but 
with multifocal sharp waves and no evidence of the typical patterns associated 
with Ohtahara or West syndrome. Therapy with levetiracetam and oxcarbazepine 
effectively managed the seizure episodes. Investigation of genes associated with 
infantile forms of epilepsy such as SCN1A, SCN1B, and ARX were negative, but we 
identified a novel single-nucleotide duplication mutation, c.931dupT 
(p.S311FfsX3), in exon 11 of the STXBP1 gene. This previously unreported STXBP1 
mutation in a subject with neonatal-onset focal seizures broadens the spectrum 
of clinically relevant human disorders caused by STXBP1 mutations.