Epilepsy is not a mandatory feature of STXBP1 associated ataxia-tremor-retardation syndrome.

Background: Mutations in the STXBP1 gene (MUNC18-1) were first described to cause Ohtahara syndrome (Early infantile epileptic encephalopathy, EIEE)(12-14) characterized by very early infantile epileptic encephalopathy with frequent tonic spasms and a suppression-burst pattern on electroencephalogram. In the following years a wider phenotype was recognized having milder forms of epilepsies. All patients showed also intellectual disability and movement disorders.