Genetic Epilepsy with Febrile Seizures Plus (GEFS+)

Genetic epilepsy with febrile seizures plus (GEFS+) is an inherited epilepsy spectrum in which febrile seizures occur in several family members, often alongside different afebrile seizure types. The “plus” does not mean that every affected person has severe epilepsy. It refers to features extending beyond the usual pattern of simple febrile seizures.

GEFS+ is best understood as a family spectrum rather than a single identical phenotype. One relative may have only febrile seizures, another may have febrile seizures that continue beyond the usual age range, and another may develop absence, myoclonic, focal or generalised tonic-clonic seizures.

Where GEFS+ fits in ILAE classification

The International League Against Epilepsy includes GEFS+ among epilepsy syndromes with onset in neonates and infants because the first seizures commonly occur in early childhood, usually with fever.

The syndrome is genetic and often familial, but there is marked clinical variability within and between families.

What “febrile seizures plus” means

Typical simple febrile seizures usually occur between about 6 months and 5 years and stop as the child grows older.

In febrile seizures plus (FS+), febrile seizures may continue beyond the usual age range and/or the person may also experience afebrile seizures.

A spectrum, not one seizure type

GEFS+ can include several epilepsy phenotypes in the same family. Reported features include febrile seizures, FS+, generalised tonic-clonic seizures, absence seizures, myoclonic seizures, focal seizures and, in some families, more severe developmental epilepsies.

This variability is one of the defining characteristics of the syndrome.

Age at onset

Seizures typically begin in infancy or early childhood, often as febrile convulsions.

The later course varies. Some children stop having seizures by mid-childhood, while others continue to have afebrile epilepsy.

SCN1A

SCN1A is one of the best-known genes associated with GEFS+. It encodes the Nav1.1 neuronal sodium-channel subunit.

However, GEFS+ is not synonymous with SCN1A. Variants in several other genes can produce a similar familial phenotype.

Other genes

Genes reported in GEFS+ families include SCN1A, SCN1B, GABRG2, STX1B and others.

Because genetic heterogeneity is substantial, modern testing usually uses an epilepsy gene panel, exome sequencing or genome sequencing rather than testing only one gene.

Inheritance

Many GEFS+ families show autosomal-dominant inheritance, but penetrance is incomplete. This means a person can carry a pathogenic variant without developing the full epilepsy phenotype.

Severity can vary greatly even among relatives carrying the same familial variant.

Relationship to Dravet syndrome

Dravet syndrome and GEFS+ can occur within the broader SCN1A spectrum, but they are not interchangeable diagnoses.

Dravet syndrome is a developmental and epileptic encephalopathy with a characteristic early course, prolonged seizures and later developmental slowing. Most people with GEFS+ have a milder course and normal development.

EEG

EEG findings depend on the phenotype. Generalised spike-wave activity may occur in people with generalised seizure types, while focal abnormalities can be seen in some affected individuals.

A normal routine EEG does not exclude GEFS+.

MRI

MRI is usually normal in classic GEFS+.

Imaging may be appropriate when seizures have persistent focal features, neurological examination is abnormal or another structural cause is suspected.

Treatment

Treatment depends on the individual seizure types rather than the family label alone.

Some people with only infrequent febrile seizures may not require daily antiseizure medication. Others with recurrent afebrile epilepsy may need long-term treatment.

Medication selection

Broad-spectrum antiseizure medicines are commonly used when generalised seizure types are present.

If a person has an SCN1A-related phenotype approaching Dravet syndrome, medication choices may differ from those appropriate for an uncomplicated familial febrile-seizure syndrome.

Prognosis

Many affected people have a relatively favourable course, but the spectrum is broad.

The family history can include both mild febrile seizures and severe epilepsies, so prognosis should be based on the individual phenotype rather than the GEFS+ family label alone.

Genetic counselling

Identifying a familial pathogenic variant can clarify recurrence risk and may help classify relatives whose childhood seizure history is uncertain.

Because penetrance and severity are variable, genetic counselling should avoid implying that inheriting the variant predicts one exact outcome.

Worldwide diagnosis

Detailed family history remains valuable where genetic testing is unavailable. Asking whether relatives had childhood convulsions with fever, epilepsy or unexplained seizures can reveal a multigenerational pattern.

Genomic testing is increasingly accessible but remains highly unequal worldwide.

The central point

GEFS+ is a familial epilepsy spectrum, not one fixed disease pattern. The defining feature is the combination of febrile-seizure susceptibility and a wider range of epilepsy phenotypes within a family.

Sources

Medical note: fever can trigger seizures in many different epilepsies. GEFS+ diagnosis depends on the wider personal and family pattern.

Evidence checked: September 2026.