What is the definition of Dravet Syndrome?

Dravet syndrome is the most severe of a group of conditions known as SCN1A-related seizure disorders. Symptoms include seizures which first occur in infancy that are often triggered by high temperatures (febrile seizures). In childhood, many types of seizures may occur and they may increase in frequency. Seizures may be difficult to treat. Other symptoms include loss of motor skills, intellectual disability, speech impairment, and difficulty with movement. Most cases of Dravet syndrome occur when the SCN1A gene is not working correctly. It can be inherited in an autosomal dominant pattern, but most people with Dravet syndrome do not have a family history of the condition. Diagnosis is based on a clinical exam, medical history, and the results of genetic testing. The main goal of treatment is to reduce the number and length of seizures.

What are the alternative names for Dravet Syndrome?

  • Severe Myoclonic Epilepsy of Infancy
  • SMEI
  • Myoclonic epilepsy, severe, of infancy
  • SME

What are the causes for Dravet Syndrome?

Dravet syndrome occurs when the SCN1A gene is not working correctly. DNA changes known as pathogenic variants are responsible for making genes work incorrectly or sometimes, not at all.  DNA changes in the SCN1B, GABRG2, SCN2A and several other genes are associated with seizure disorders with similar symptoms to Dravet syndrome. 

What are the symptoms for Dravet Syndrome?

The following list includes the most common signs and symptoms in people with Dravet syndrome. These features may be different from person to person. Some people may have more symptoms than others and symptoms can range from mild to severe. This list does not include every symptom or feature that has been described in this condition. Signs and symptoms include: 
  • Many different types of seizures
  • Sudden muscle jerking (myoclonus)
  • Loss of developmental skills
  • Intellectual disability
  • Problems with walking
  • Speech impairment
  • Autistic-like behavior
The first seizures appear before one year of age and are often associated with fevers. In childhood, other types of seizures develop, and the frequency of seizures increases. Loss of developmental and cognitive skills may occur along with speech impairment and difficulty walking. In adulthood, the number of seizures may decrease, and nighttime seizures may occur. More serious complications include the risk of continuous seizures (status epilepticus) and sudden unexplained death.

Is Dravet Syndrome an inherited disorder?

In some cases, Dravet syndrome is inherited in an autosomal dominant pattern. All individuals inherit two copies of each gene. Autosomal means the gene is found on one of the numbered chromosomes found in both sexes. Dominant means that only one altered copy of a gene is necessary to have the condition. The alteration can be inherited from either parent. Dravet syndrome usually occurs due to a new genetic change that occurs for the first time in a person and is not present in either parent (de novo mutation).    Each child of an individual with an autosomal dominant condition has a 50% or 1 in 2 chance of inheriting the alteration and the condition. Typically, children who inherit a dominant alteration will have the condition, but they may be more or less severely affected than their parent. Sometimes a person may have a gene alteration for an autosomal dominant condition and show no signs or symptoms of the condition.