A seizure triggered by fever in a young child — and, for two of this page's five variants, one specific to seizures after the MMR vaccine, at a gene that is literally the measles virus's own entry point into human cells.
Febrile seizures are convulsions triggered by fever, most common in children between 6 months and 5 years old. They are usually brief and not associated with lasting harm, but they are frightening to witness and, in a small proportion of cases, follow vaccination specifically. This page holds 5 variants from one study that deliberately separated those two situations genetically.
A 2014 study did not look for "the febrile seizure gene." It ran a series of genome-wide association scans comparing three distinct groups: children with febrile seizures specifically following MMR (measles, mumps, rubella) vaccination, children with febrile seizures unrelated to any vaccination, and controls with no history of seizures at all — structured precisely to tell apart a vaccination-specific genetic signal from a general one.
Two loci were distinctly associated with febrile seizures following MMR vaccination and not with febrile seizures in general: rs273259, in IFI44L — an interferon-stimulated gene, part of the body's antiviral immune response — and rs1318653, near CD46. The CD46 connection is specific and worth stating plainly: CD46 is, independently of this study, the actual cell-surface receptor the measles virus binds to enter human cells. A variant near the virus's own entry point predicting who seizes after a vaccine built around a weakened version of that same virus is a mechanistically coherent finding, not a coincidence the paper leaves unexplained.
Separately, four loci were associated with febrile seizures in general, regardless of vaccination status: two sodium channel genes, SCN1A (not on this page) and SCN2A — sodium channels are directly relevant to seizure biology, controlling the electrical excitability of neurons — a gene in the TMEM16 family called ANO3 (not on this page, though the same paper confirmed its relevance with electrophysiology experiments in rats), and a region at chromosome 12q21.33 the paper associates with magnesium levels, near ATP2B1, the source of this page's rs11105468.
Positions joined since this page was written
What this is The text above discusses the variants this page was written around. Since then the catalogue has joined 6 more positions to it, by shared trait or shared paper. They are listed here by the paper each came from; the text does not describe them, and each variant page carries that study's own record.
Skotte L et al. 2022, Brain : a journal of neurology rs1518111 (IL10), rs4974130 (ERC2), rs3001038 (near LINC01788), rs244620 (near TMEM183AP4) — PMID:35022648
Feenstra B et al. 2014, Nature genetics rs13004083 (SCN1A), rs2724384 (CD46) — PMID:25344690
2026-02-04 · Anderson SA, et al. (FDA), Vaccine 2026, PMID:41643233
Verified directly against the paper's own abstract via Europe PMC (PMID:41643233, published online 4 Feb 2026, print March 2026). A self-controlled case series across three US commercial insurance databases found a statistically significant increased incidence of febrile seizure in the 0-1 days after monovalent mRNA-1273 (Moderna) vaccination in children aged 2-5 (incidence rate ratio 2.52); the BNT162b2 (Pfizer) vaccine showed an elevated but non-significant increase. The authors, including FDA scientists, concluded the monovalent mRNA vaccines' overall safety profile 'remains favorable' for young children despite this signal. Filed at the condition level, not against this page's own variants (matches.variants left empty): this study is about a different vaccine (COVID-19 mRNA, not MMR) and did not test the IFI44L/CD46 loci this page describes for MMR-specific febrile seizures -- a related real-world safety signal for the same clinical outcome, not a genetic finding, and graded 'plausible' rather than 'confirmed' for that reason.
Febrile seizures are diagnosed clinically, from a fever accompanying a convulsion in a young child with no other explanation found — not by genotype. None of the 5 variants on this page are used by any guideline to diagnose febrile seizures, predict them, or decide vaccination.
The loci described above come from a population-level genetic study distinguishing two situations at once — general febrile-seizure susceptibility, and susceptibility specific to the MMR vaccine. They point at which biological systems (sodium-channel excitability for the general case; antiviral immune response and the measles receptor itself for the MMR-specific case) shape risk at a population level. They do not predict whether any individual child will have a febrile seizure, with or without vaccination — and febrile seizures following MMR vaccination remain rare and are not, on their own, a reason to avoid vaccination, which the study's own design (comparing MMR-related and general febrile seizures as separate categories) was built to investigate scientifically, not to discourage.
What a 23andMe/AncestryDNA export or raw VCF can and can't tell you about Febrile Seizures comes down to these specific, well-studied positions — not a diagnosis.
The studies behind these variants recruited participants from different ancestries — a result found in one population doesn't always transfer to another. Based on 7 of 11 linked studies with a resolved discovery ancestry.
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Febrile Seizures. MyGeneLog™. https://www.mygenelog.com/conditions/febrile-seizures
Convulsions triggered by fever, most common in children between 6 months and 5 years old. Usually brief and without lasting harm.
A small proportion follow MMR vaccination specifically, and a 2014 genetic study found two loci -- one in IFI44L, one near CD46 -- associated with MMR-related seizures but not with febrile seizures in general, suggesting a distinct, immune/virus-related mechanism for that specific case.
CD46 is, independently of this genetic study, the actual cell-surface receptor the measles virus uses to enter human cells -- a variant near this gene predicting MMR-related seizure risk is a mechanistically specific finding, not just a statistical association.
No. Febrile seizures are diagnosed clinically. These are population-level genetic findings, not a way to predict an individual case, and they are not used in any guideline about vaccination decisions.
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.