STXBP1-Related Syndrome

STXBP1-related syndrome happens when there are changes to the STXBP1 gene. These changes can keep the gene from working as it should.

Each family is different. A geneticist or genetic counselor can give you advice on the chance that this will happen again in your family.

The risk of having another child who has STXBP1-related syndrome depends on the genes of both biological parents. 

• If neither biological parent has the same genetic variant found in their child, the chance of having another child who has the syndrome is on average 1 percent. This 1 percent chance is higher than the chance of the general population. The increase in risk is due to the very unlikely chance that more of the mother’s egg cells or the father’s sperm cells carry the same genetic variant. 
• If one biological parent has the same genetic variant found in their child, the chance of having another child who has the syndrome is 50 percent. 

For a symptom-free brother or sister of someone who has STXBP1-related syndrome, the sibling’s risk of having a child who has STXBP1-related syndrome depends on the sibling’s genes and their parents’ genes. 

• If neither parent has the same genetic variant causing STXBP1-related syndrome, the symptom-free sibling has a nearly 0 percent chance of having a child who would inherit STXBP1-related syndrome. 
• If one biological parent has the same genetic variant causing STXBP1-related syndrome, the symptom-free sibling has a 50 percent chance of also having the same genetic variant. If the symptom-free sibling has the same genetic variant, their chance of having a child who has the genetic variant is 50 percent. 

For a person who has STXBP1-related syndrome, the risk of having a child who has the syndrome is about 50 percent.

As of 2026, over 600 people in the world with changes in the STXBP1 gene have been described in medical research. The first case of STXBP1-related syndrome was described in 2008. Scientists expect to find more people who have the syndrome as access to genetic testing improves.

Scientists and doctors have only just begun to study STXBP1-related syndrome. At this point, there are no medicines designed to treat the syndrome. A genetic diagnosis can help people decide on the best way to track the condition and manage therapies. Doctors can refer people to specialists for:

• • Physical exams and brain studies
  • Genetics consults
  • Development and behavior studies
  • Other issues, as needed

A developmental pediatrician, neurologist, or psychologist can follow progress over time and can help:

• • Suggest the right therapies. This can include physical, occupational, speech, or behavioral therapy.
  • Guide individualized education plans (IEPs).

Specialists advise that therapies for STXBP1-related syndrome should begin as early as possible, ideally before a child begins school.

If seizures happen, consult a neurologist. There are many types of seizures, and not all types are easy to spot. To learn more, you can refer to resources such as the Epilepsy Foundation’s website: www.epilepsy.com/learn/types

Learning and Speech

People with STXBP1-related syndrome had developmental delay or intellectual disability, and speech delay or impairment. About 1 in 10 children had a developmental regression.

• 487 out of 534 people had developmental delay or intellectual disability (91 percent)
• 258 out of 534 people had speech delay or impairment (48 percent)
• 56 out of 534 people had a developmental regression (11 percent)

Behavior

Some people with STXBP1-related syndrome had behavioral issues, such as autism or features of autism, hyperactivity or attention-deficit/hyperactivity disorder (ADHD), and self-injury behavior.

• 86 out of 534 people had autism or features of autism (16 percent)
• 22 out of 534 people had hyperactivity or ADHD (4 percent)
• 13 out of 534 people had self-injury behavior (2 percent)

Brain

People with STXBP1-related syndrome had seizures, low muscle tone (hypotonia), brain changes seen on magnetic resonance imaging (MRI), or movement issues, such as ataxia, tremor, dystonia, hypomimia, bradykinesia, dyskinesia, or choreoathetosis.

About 1 in 5 people were unable to walk. Some people had seizures even though they were on pain medications (refractory seizures).

Some researchers have suggested that adults with STXBP1-related syndrome have a much higher rate of refractory seizures and movement disorders than children with the condition.

• 474 out of 534 people had seizures (89 percent)
• 73 out of 534 people had refractory seizures (14 percent)
• 216 out of 534 people had hypotonia (40 percent)
• 128 out of 534 people had ataxia (24 percent)
• 82 out of 534 people had tremor (15 percent)
• 28 out of 534 people had dystonia (5 percent)
• 108 out of 534 people were unable to walk (20 percent)

The most common seizure types were focal-onset seizures, generalized-onset seizures, and infantile spasms. Seizure onset typically occurred within the first year of life. Several people experienced more than one seizure type. Other common seizure types included:

• Infantile spasms
• Generalized tonic
• Generalized tonic-clonic
• Focal impaired awareness
• Generalized myoclonic
• Focal clonic
• Focal tonic
• Focal motor

Vision

Some people with STXBP1-related syndrome had vision issues, including uncontrolled eye movements (nystagmus), crossed eyes (strabismus), and cerebral visual impairment.

• 51 out of 534 people had vision issues (10 percent)

Gastrointestinal

People with STXBP1-related syndrome had gastrointestinal issues, such as gastroesophageal reflux disease (GERD), gastrostomy tube feeding in infancy, feeding difficulties, and constipation.

• 25 out of 534 people had GERD (5 percent)
• 14 out of 534 people had gastrostomy tube feeding in infancy (3 percent)
• 16 out of 534 people had feeding difficulties (3 percent)

STXBP1 Foundation

STXBP1 Foundation is dedicated to finding a cure for STXBP1-Related Disorders (STXBP1-RD) while improving the lives of our patients and families. Founded in 2017, STXBP1 Foundation is a parent-led advocacy organization. STXBP1-RD is a rare neurodevelopmental disorder caused by changes in the STXBP1 gene. With an incidence of approximately 1 in 30,000 live births, STXBP1-RD is one of the most common genetic causes of epilepsy.

• STXBP1 Foundation Website – stxbp1disorders.org
• STXBP1 Foundation – Facebook page

Simons Searchlight

Simons Searchlight is an online international research program, building an ever growing natural history database, biorepository, and resource network of over 175 rare genetic neurodevelopmental disorders. By joining their community and sharing your experiences, you contribute to a growing database used by scientists worldwide to advance the understanding of your genetic condition. Through online surveys and optional blood sample collection, they gather valuable information to improve lives and drive scientific progress. Families like yours are the key to making meaningful progress. To register for Simons Searchlight, go to the Simons Searchlight website at www.simonssearchlight.org and click “Join Us.”

• Learn more about Simons Searchlight – www.simonssearchlight.org/frequently-asked-questions
• Simons Searchlight webpage with more information on STXBP1 – www.simonssearchlight.org/research/what-we-study/stxbp1
• Simons Searchlight STXBP1 Facebook community – Simons Searchlight STXBP1 Facebook community

Other resources:

• Unique – STXBP1 Guidebook
• Geisinger Developmental Brain Disorder Gene Database – STXBP1