GENE GUIDE

SCN1A-Related Syndrome

This guide is not meant to take the place of medical advice. Please consult with your doctor about your genetic results and health care choices. This Gene Guide was last updated in 2024. As new information comes to light with new research we will update this page. You may find it helpful to share this guide with friends and family members or doctors and teachers of the person who has SCN1A-Related Syndrome.
a doctor sees a patient

SCN1A-related syndrome is also called Dravet syndrome, developmental and epileptic encephalopathy 6B (DEE6B), and generalized epilepsy with febrile seizures plus, type 2 (GEFSP2). For this webpage, we will be using the name SCN1A-related syndrome to encompass the wide range of variants observed in the people identified.

SCN1A-related syndrome happens when there are changes in the SCN1A gene. These changes can keep the gene from working as it should.

Key Role

The SCN1A gene produces a protein that sits in the surface of brain cells and allows sodium to enter the cell. This protein is important for brain cells to make and transmit signals between cells. The protein is essential for these brain cells to work properly.

Symptoms

Because the SCN1A gene is important for brain activity, many people who have SCN1A-related syndrome have:

  • Epilepsy
  • Developmental delay
  • Intellectual disability
  • Autism spectrum disorder or features of autism
  • Movement problems
  • Concerns with sleep
  • Vision issues
  • Speech impairment
  • Low muscle tone
  • Brain changes seen on magnetic resonance imaging (MRI)

SCN1A-related syndrome is a genetic condition, which means that it is caused by variants in genes. Our genes contain the instructions, or code, that tell our cells how to grow, develop, and work. Every child gets two copies of the SCN1A gene: one copy from their mother’s egg, and one copy from their father’s sperm. In most cases, parents pass on exact copies of the gene to their child. But the process of creating the egg or sperm is not perfect. A change in the genetic code can lead to physical issues, developmental issues, or both. 

Sometimes a spontaneous variant happens in the sperm, egg or after fertilization. When a brand new genetic variant happens in the genetic code is called a ‘de novo’ genetic variant. The child is usually the first in the family to have the genetic variant.

De novo variants can take place in any gene. We all have some de novo variants, most of which don’t affect our health. But because SCN1A plays a key role in development, de novo variants in this gene can have a meaningful effect. 

Research shows that SCN1A-related syndrome is often the result of a de novo variant in SCN1A. Many parents who have had their genes tested do not have the SCN1A genetic variant found in their child who has the syndrome. In some cases, SCN1A-related syndrome happens because the genetic variant was passed down from a parent.

Autosomal dominant conditions

SCN1A-related syndrome is an autosomal dominant genetic condition. This means that when a person has the one damaging variant in SCN1A they will likely have symptoms of SCN1A-related syndrome. For someone with an autosomal dominant genetic syndrome, every time they have a child there is a 50 percent chance they pass on the same genetic variant and a 50 percent chance they do not pass on the same genetic variant.

Autosomal Dominant Genetic Syndrome

GENE / gene
GENE / gene
Genetic variant that happens in sperm or egg, or after fertilization
GENE / gene
Child with de novo genetic variant
gene / gene
Non-carrier child
gene / gene
Non-carrier child

Why does my child have a change in the SCN1A gene?

No parent causes their child’s SCN1A-related syndrome. We know this because no parent has any control over the genetic changes that they do or do not pass on to their children. Please keep in mind that nothing a parent does before or during the pregnancy causes this to happen. The genetic change takes place on its own and cannot be predicted or stopped.

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 SCN1A-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 SCN1A-related syndrome, the sibling’s risk of having a child who has SCN1A-related syndrome depends on the sibling’s genes and their parents’ genes. 

  • If neither parent has the same genetic variant causing SCN1A-related syndrome, the symptom-free sibling has a nearly 0 percent chance of having a child who would inherit SCN1A-related syndrome. 
  • If one biological parent has the same genetic variant causing SCN1A-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 SCN1A-related syndrome, the risk of having a child who has the syndrome is about 50 percent.

SCN1A-related syndrome occurs in 1 in every 20,900 births. As of 2026, over 1,100 people with SCN1A-related syndrome have been reported in medical research. The first case of SCN1A-related syndrome was described in 2000.

People with SCN1A-related syndrome may look different. Appearance can vary and can include, but is not limited to, these features:

  • Smaller than average head size (microcephaly)
  • Low muscle tone

Scientists and doctors have only just begun to study SCN1A-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 SCN1A-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-seizures.

This section includes a summary of information from published articles. It highlights how many people have different symptoms. To learn more about the articles, see the Sources and references section of this guide.

The majority of people with SCN1A-related syndrome have SCN1A genetic variants that occurred de novo or spontaneously in that person and were not found in their parents. However, in the medical research, about 1 in 10 people with SCN1A-related syndrome had inherited the variant from one parent.

Of the SCN1A carrier parents, many were identified to be mosaic for an SCN1A variant. Being mosaic for a genetic variant means that a person has some cells with the genetic variant and other cells that do not have the genetic variant. People who are mosaic for a genetic variant have a genetic change that happened after conception, but usually during the earlier stages of pregnancy. These variants happen spontaneously and are not a result of something that happened or was taken during pregnancy.

Learning

People with SCN1A-related syndrome had mild to severe developmental delay.

Behavior

People with SCN1A-related syndrome had behavioral issues, such as autism or features of autism, inattention, impulsivity, anxiety, and obsessive personality traits.

  • 45 out of 1,061 people had features of autism (4 percent)

Brain

Most people with SCN1A-related syndrome had seizures, with the average age of onset around 6 months. The most frequent seizure types included generalized tonic-clonic seizures, hemi-clonic seizures, focal seizures, myoclonic seizures, and atypical absence seizures.

  • 1,004 out of 1,061 people had generalized tonic-clonic seizures (95 percent)
  • 992 out of 1,061 people had hemi-clonic seizures (93 percent)
  • 923 out of 1,061 people had focal seizures (87 percent)
  • 674 out of 1,061 people had myoclonic seizures (64 percent)
  • 324 out of 1,061 people had atypical absence seizures (31 percent)

A few people had brain changes seen on magnetic resonance imaging (MRI), such as one-sided or both-sided brain atrophy (shrinkage) or abnormal signal in the hippocampus.

  • 93 out of 1,061 people had brain changes seen on MRI (9 percent)
Human head showing brain outline

Mobility

People with SCN1A-related syndrome had hypotonia, incoordination, and limited ability to move their hands. Children over the age of 5 tended to develop a crouched walking stance.

SCN1A conditions

People with a problematic SCN1A genetic variant (a pathogenic or likely pathogenic variant) usually develop clinical features. The subtype of the SCN1A condition a person has is determined by their clinical picture, which includes but is not limited to the following diagnoses.

  • Febrile seizures: Childhood seizures that happen in association with fever. For some people, febrile seizures resolve by age 5. People with febrile seizures plus (FS+) have a persistence of febrile seizures beyond age 6 and may have other seizures types.
  • Generalized epilepsy with febrile seizures plus (GEFS+): GEFS+ is usually a diagnosis assigned to a family where a problematic SCN1A variant is inherited by several members in a family. Families with a GEFS+ diagnosis have symptoms that vary in each individual family member. Features include a spectrum from febrile seizures to medically treatable generalized epilepsy, intractable generalized epilepsy, or Dravet syndrome.
  • Dravet syndrome: Guidelines for the diagnosis of Dravet syndrome include the development of seizures between 12 months and 18 months of age after initial typical development. An SCN1A genetic variant is the most common genetic diagnosis of people with Dravet syndrome. But, several other genes have been associated with a clinical Dravet syndrome diagnosis. Seizures are common, including recurrent generalized tonic-clonic, hemiconvulsive, or myoclonic. Seizures can be triggered by a hot bath, physical exertion, fever following vaccination, light stimuli, or sodium channel-blocking anti-seizure medication. Seizures tend to lessen in severity after puberty, but they rarely go away completely.
  • Intractable childhood epilepsy with generalized tonic-clonic seizures (ICE-GTC): This is defined as generalized seizures, including absence seizures and generalized tonic-clonic seizures, with onset in infancy or childhood. The difference between ICE-GTC and Dravet syndrome is not completely clear.

Research indicates that people with SCN1A-related syndrome are at risk of sudden unexpected death in epilepsy (SUDEP). In general, SUDEP is the leading cause of death in people with uncontrolled seizures.

Where can I find support and resources?

Dravet Syndrome Foundation

The mission of Dravet Syndrome Foundation (DSF) is to aggressively raise funds for Dravet syndrome and related epilepsies; to support and fund research; increase awareness; and to provide support to affected individuals and families.

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.”

Sources and References

The content in this guide comes from published studies about SCN1A-related syndrome. Below you can find details about each study, as well as links to summaries or, in some cases, the full article.

  • Ding, J., Li, X., Tian, H., Wang, L., Guo, B., Wang, Y., Li, W., Wang, F., & Sun, T. (2021). SCN1A mutation-beyond Dravet syndrome: A systematic review and narrative synthesis. Frontiers in Neurology, 12, 743726. doi:10.3389/fneur.2021.743726
  • He, M., Min, X., Shu, J., Wu, B., Qi, H., Wang, X., & Zhang, G. (2026). Clinical characteristics and genetic analysis of patients with SCN1A gene pathological variant-related disorders: A single-center retrospective study. Italian Journal of Pediatrics, Epub ahead of print. doi:10.1186/s13052-026-02269-8
  • Miller, I. O., & Sotero de Menezes, M. A. SCN1A seizure disorders. 2022 Feb 17. In: Adam MP, Bick S, Mirzaa GM, et al., editors. GeneReviews® [Internet]. Seattle (WA): University of Washington, Seattle; 1993-2026. Available from: https://www.ncbi.nlm.nih.gov/books/NBK1318/
  • Tian, X., Cheng, M., Yang, Y., Zeng, Q., Chen, Y., Liu, A., Yang, X., Zhang, J., Tan, Q., … & Zhang, Y. (2026). Genotypic spectrum in 1215 patients with Dravet syndrome or Dravet syndrome-like phenotype. Pediatric Research, Epub ahead of print. doi:10.1038/s41390-026-04790-2
  • Sullivan, J., Benítez, A., Roth, J., Andrews, J. S., Shah, D., Butcher, E., Jones, A., & Cross, J. H. (2024). A systematic literature review on the global epidemiology of Dravet syndrome and Lennox-Gastaut syndrome: Prevalence, incidence, diagnosis, and mortality. Epilepsia, 65(5), 1240-1263. doi:10.1111/epi.17866