STXBP1-related disorder is a neurodevelopmental condition caused by pathogenic variants in STXBP1, a gene essential for synaptic vesicle release. Epilepsy is common but not universal, and developmental impairment is a core feature of the disorder.
What STXBP1 does
STXBP1 encodes Munc18-1, a protein required for synaptic vesicle docking and neurotransmitter release.
Most disease-causing variants reduce the amount or function of the protein.
Seizure onset
Seizures often begin in the first weeks or months of life, although later onset can occur.
Infantile spasms, focal seizures, tonic seizures, myoclonic seizures, atonic seizures and generalised tonic-clonic seizures have all been reported.
EEG
EEG can show focal epileptiform abnormalities, burst suppression, hypsarrhythmia or generalised spike-and-wave activity.
No single EEG pattern defines STXBP1-related disease.
Developmental impairment
Developmental delay is universal or nearly universal in clinically recognised STXBP1-related disorder.
Intellectual disability ranges from mild to profound, and speech is often more severely affected than gross motor development.
Movement disorders
Tremor, ataxia, dystonia, dyskinesia, choreiform movements and stereotypies are common.
These movements can be mistaken for seizures, making video review and EEG correlation important.
Epilepsy can improve while disability persists
Some people experience spontaneous seizure remission or substantial reduction over time.
Developmental and movement difficulties can remain even when epilepsy becomes less active, showing that STXBP1 is not simply an epileptic encephalopathy.
Treatment
There is no universally effective antiseizure medicine for STXBP1-related epilepsy.
Treatment is individualised according to seizure type and response.
Evidence from cohorts
Retrospective studies have reported benefit from medicines including phenobarbital and clobazam, and from ketogenic dietary therapy in some people.
The evidence is not strong enough to claim one proven gene-specific first-line treatment.
Infantile spasms
When infantile epileptic spasms syndrome is present, syndrome-specific first-line therapy remains important regardless of the STXBP1 diagnosis.
This can include hormonal treatment and/or vigabatrin depending on the clinical context.
Genetics
Most affected people have a de novo heterozygous pathogenic variant.
Rare parental mosaicism can occur and may influence recurrence risk.
Precision therapy research
STXBP1 is a major gene-therapy research target. Strategies under investigation include gene replacement, increasing expression of the healthy copy, antisense approaches and other methods of restoring Munc18-1 function.
These therapies remain experimental.
Care beyond epilepsy
Management can involve physiotherapy, communication support, feeding assessment, sleep management, movement-disorder care and behavioural support.
Families often identify communication and development as priorities alongside seizure control.
Worldwide access
Broad genetic testing is often needed because STXBP1 cannot be reliably diagnosed from seizure type alone.
Access to molecular diagnosis and multidisciplinary therapies varies substantially worldwide.
The central point
STXBP1-related disorder is a synaptic neurodevelopmental condition in which epilepsy is important but only one part of the phenotype.
Related reading
IESS →
Genetic Testing in Epilepsy →
Sources
- GeneReviews — STXBP1 Encephalopathy with Epilepsy
- 2026 review — STXBP1 precision therapeutic strategies
Medical note: abnormal movements in STXBP1-related disorder are not always seizures and may require video-EEG or movement-disorder assessment.
Evidence checked: September 2026.