One gene, SCN1A, appears twice in this page and means something different each time: a common variant that shifts risk a little, and a rare change that causes severe epilepsy in a child. Telling those two apart is most of what genetics can offer here.
A seizure is what happens when a population of neurons fires together when it should not. Epilepsy is the tendency to have them repeatedly without an obvious external cause, and it is common: roughly 50 million people live with it worldwide, and about 1 person in 100 will be diagnosed at some point.
It is not one disease. It is a category holding conditions with quite different causes — a stroke, a head injury, a brain malformation, an infection, an autoimmune process, and in a large share of cases nothing identifiable at all. Genetics matters in some of those and not in others, and the honest first sentence is that most people with epilepsy do not have a genetic explanation anybody can name.
Two completely different research programmes both produce sentences with "epilepsy" and a gene in them, and they mean different things.
Rare and powerful. A small number of children have epilepsy caused by a single change with a large effect. The best known is SCN1A: a loss-of-function change there causes Dravet syndrome, a severe epilepsy beginning in the first year of life. These are found by sequencing an affected child, they are usually new in that child rather than inherited, and finding one changes clinical decisions — including which drugs to avoid.
Common and weak. Genome-wide studies scan hundreds of thousands of people for positions that differ slightly between those with epilepsy and those without. They find real associations, and each one shifts risk by a small amount. The positions on this page come from that second kind of study.
SCN1A appears in both. The same gene carries rare changes that cause a severe childhood epilepsy, and common variants that nudge the risk of epilepsy in general. Reading a common SCN1A variant as though it meant Dravet syndrome would be a serious error, and it is the error this page exists to prevent.
The largest study behind these pages pooled genome-wide data across all epilepsies and reported associations including SCN1A, PCDH7 and a position near MMP8. A separate study of genetic generalised epilepsy reported a locus near VRK2. These are population findings. None of them is a test, none is diagnostic, and carrying any of them is entirely compatible with never having a seizure.
This is the part of the page with real consequences, and it is about medicines rather than about causes.
Nothing here should be used to start, stop or change an antiseizure medicine. Stopping one abruptly is dangerous.
How epilepsy is diagnosed. By history first — what happened, what it looked like, what came before it — supported by EEG and usually by MRI. There is no genetic test that diagnoses epilepsy, and a normal EEG does not exclude it.
When genetic testing is offered. Mainly in epilepsies beginning in infancy or early childhood, in epilepsy with developmental delay, and where a specific syndrome is suspected. Panels and exome sequencing look for rare changes with large effects. That is a different test from a consumer genotyping array, which cannot see most of them.
SCN1A specifically. It encodes part of a sodium channel. Loss-of-function changes cause Dravet syndrome and milder changes cause the GEFS+ spectrum. The clinical importance is not only the diagnosis: sodium-channel-blocking drugs can worsen seizures in Dravet syndrome, so knowing the cause changes the prescription.
Inheritance. Most epilepsy does not follow a simple pattern. Having a first-degree relative with epilepsy raises risk somewhat, and the absolute risk stays low. The rare severe forms are frequently caused by changes that arose new in the affected child, which is why they can appear in a family with no history at all.
What a 23andMe/AncestryDNA export or raw VCF can and can't tell you about Epilepsy comes down to these specific, well-studied positions — not a diagnosis.
HACE1 · rs71568191
See detailed info →Almost certainly not on that basis. These come from studies comparing large groups, and each position shifts risk by a small amount. They are not a test, and carrying one is entirely compatible with never having a seizure.
No, and this is the most important misreading to avoid. Dravet syndrome is caused by rare changes that disable the gene, found by sequencing. A common SCN1A variant reported by a consumer array is a different kind of finding entirely and does not indicate it.
It can rule one out in a specific case. HLA-B*15:02 carriers face a substantially raised risk of severe skin reactions on carbamazepine, oxcarbazepine and phenytoin, and testing before starting is recommended where that allele is common. Beyond that, choice of medicine is clinical.
Sometimes, and rarely in a simple way. A close relative with epilepsy raises risk somewhat while the absolute risk stays low. The severe childhood forms are often caused by a change that arose new in that child, so they appear in families with no history.
Free to reuse. This page's text is original writing from freely-available research, licensed CC BY 4.0 — reuse it, including commercially, with attribution to MyGeneLog. It's general research-derived information, not medical advice or a diagnosis — see Terms of Use.