A febrile seizure is a convulsion in a young child triggered by a fever. These events are most common between the ages of six months and five years and are often caused by a viral infection. While witnessing a febrile seizure can be frightening for any parent, they are not harmful to the child. A frequent question for concerned caregivers is whether these seizures have a genetic component or “run in the family.” This article will explore the evidence for a genetic link, discussing family history, specific genes, and how this information influences medical guidance.
The Role of Family History
When a child has a febrile seizure, one of the first things a healthcare provider will ask about is family history. Studies show a strong hereditary influence, with genetics accounting for a significant portion of a child’s susceptibility. Research involving twins has provided powerful evidence for this genetic link. In these studies, identical (monozygotic) twins, who share nearly all of their DNA, are much more likely to both have a history of febrile seizures compared to fraternal (dizygotic) twins.
If a parent or sibling has a history of febrile seizures, the child’s own risk is higher than that of the general population, with some studies suggesting the risk is two to three times more common.
It is important to understand that while a family history increases the probability, it does not guarantee a child will have a febrile seizure. Many children who experience these events have no known family history of them, indicating that environmental triggers like specific viral illnesses are also involved.
Identified Genes and Genetic Syndromes
Scientists have pinpointed several specific genes that are associated with an increased likelihood of having febrile seizures. Many of these genes are involved in the function of ion channels in the brain, which are like gates on nerve cells that control the flow of electrically charged particles. Changes in these genes can make the brain more susceptible to the effects of a fever.
Two of the most well-studied genes are SCN1A and GABRG2. The SCN1A gene provides instructions for making a part of a sodium channel, which allows sodium ions into neurons and plays a part in generating electrical signals. The GABRG2 gene is involved in creating a receptor for a neurotransmitter called GABA, which has a calming or inhibitory effect on the brain’s electrical activity. Variations in these genes can disrupt the normal balance of excitation and inhibition in the brain, a balance that can be further disturbed by a high temperature.
In a small number of families, these genetic variations can lead to a specific inherited condition called Genetic Epilepsy with Febrile Seizures Plus (GEFS+). GEFS+ is a spectrum disorder where family members can experience a range of seizure types. Some individuals may only have typical febrile seizures, while others might have febrile seizures that continue past the usual age of five, or they may develop other types of seizures without a fever. GEFS+ demonstrates a clear pattern of inheritance, but it is rare, and most children with febrile seizures do not have this syndrome.
Distinguishing Seizure Types and Future Risk
Not all febrile seizures are the same, and doctors classify them into two main categories: simple and complex. This distinction is based on the seizure’s characteristics and is relevant when considering a child’s future risk. A simple febrile seizure is generalized, meaning it affects the entire body, lasts for less than 15 minutes, and does not happen again within a 24-hour period; the vast majority of febrile seizures fall into this category. A seizure is defined as complex if it lasts longer than 15 minutes, is focal (confined to one part of the body), or recurs within 24 hours.
A primary concern for parents is whether a febrile seizure means their child will develop epilepsy, a condition characterized by recurrent seizures without a fever. For a child who has had a simple febrile seizure, the risk of developing epilepsy is only slightly higher than that of the general population. The risk increases for children who have experienced a complex febrile seizure, have pre-existing developmental delays, or a family history of epilepsy.
The Purpose of Genetic Testing
Given the known genetic links, parents may wonder if their child should undergo genetic testing. For a child who has experienced a single, simple febrile seizure and is otherwise developing normally, genetic testing is not recommended. In these cases, the results are unlikely to change the medical advice or treatment plan, which is focused on managing fevers and providing reassurance.
Genetic testing may be considered in more specific circumstances. If a child has complex febrile seizures, recurrent seizures, or if there is a strong family history of epilepsy that suggests a condition like GEFS+, a doctor might suggest testing. Identifying a specific genetic variant can sometimes help clarify the diagnosis and provide information about the prognosis.
For families where a syndrome like GEFS+ is suspected, genetic testing can confirm the diagnosis and help other family members understand their own potential risks. The decision to proceed with genetic testing is complex and should be made in consultation with a pediatric neurologist or a genetic counselor.