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.

Methods: Here, we present three female patients with an ataxia-tremor-retardation syndrome caused by a de novo STXBP1 mutation. Two of the girls were diagnosed through next-generation-sequencing as mutations in STXBP1 were not suspected. The third patient was diagnosed by targeted genetic testing due to its clinical features strikingly similar to the first two girls.

Results: The characteristic feature of our three patients is the lack of epilepsy which is in contrast to the majority of the patients with STXBP1 mutation.

Conclusion: Hence, epilepsy is not a mandatory feature of patients with a STXBP1 mutation.