| Phenotype category | Description (with key age ranges) | Suggested HPO terms | Frequency/statistics if available | Evidence source context IDs |
|---|---|---|---|---|
| Febrile seizures (FS) | Typical febrile seizures in otherwise neurologically normal children; usually occur from 6 months to 5 years, and in GEFS+ families may cease by 6 years; one review notes GTCS with fever commonly occur between 3 months and 6 years, with many patients having seizure termination in mid-childhood (average ~11 years). | HP:0002373 Febrile seizures; HP:0002069 Generalized tonic-clonic seizure | FS occurred in 41% of 201 individuals from 31 GEFS+ families; median onset 12 months; remission reported at 2 years in one study; febrile seizures affect ~3% of all children and 2–4% in another summary; GEFS+ pedigrees show penetrance ~60%, and one family 89% / another report ~80% (pqac-00000018, pqac-00000017, pqac-00000020, pqac-00000003, pqac-00000007) | (pqac-00000017, pqac-00000018, pqac-00000020, pqac-00000003, pqac-00000007) |
| Febrile seizures plus (FS+) | FS+ differs from typical FS because febrile attacks continue beyond age 6 years and/or include afebrile tonic-clonic seizures; can include: (1) FS lasting >6 years, (2) GTCS beyond FS, or (3) only FS after age 6. | HP:0011172 Febrile seizures plus; HP:0002069 Generalized tonic-clonic seizure | FS+ occurred in 20% of 201 individuals from 31 GEFS+ families; median onset 14 months; remission reported from 6 to 34 years; GEFS+ severity category 3 in a 2025 commentary defined as FS persisting after 6 years or associated with afebrile generalized seizures (pqac-00000018, pqac-00000019, pqac-00000015) | (pqac-00000018, pqac-00000019, pqac-00000015) |
| Afebrile generalized seizures | GEFS+ includes afebrile seizures in addition to fever-associated seizures; generalized seizure phenotypes reported include tonic-clonic, myoclonic, absence, and atonic seizures, and more severe phenotypes such as myoclonic-astatic epilepsy. | HP:0002069 Generalized tonic-clonic seizure; HP:0002123 Myoclonic seizure; HP:0002121 Absence seizure; HP:0002120 Atonic seizure | About one-third of affected individuals in one classic family series had additional seizure types beyond FS/FS+; GEFS+ combined SCN1A/SCN1B mutation frequency in familial cases was 17% in one 2001 cohort, illustrating genetic heterogeneity rather than phenotype frequency (pqac-00000007, pqac-00000019, pqac-00000020) | (pqac-00000007, pqac-00000019, pqac-00000020) |
| Afebrile focal seizures | Later nomenclature shifted from “generalized” because many patients experience focal seizures; recent review states FS+ may occur with or without focal seizures. | HP:0007359 Focal-onset seizure | No robust phenotype frequency retrieved in current evidence; focal seizures are part of the accepted spectrum (pqac-00000017, pqac-00000015) | (pqac-00000017, pqac-00000015) |
| Mixed/complex seizure presentations | GEFS+ may present as FS/FS+ with absence, myoclonic, focal, or dystonic seizures; severe end of spectrum can include myoclonic sudden epilepsy, severe myoclonic epilepsy in infants/Dravet syndrome, and myoclonic-atonic epilepsy. | HP:0002123 Myoclonic seizure; HP:0002121 Absence seizure; HP:0007359 Focal-onset seizure; HP:0001250 Seizures | Phenotypic severity in one 2025 analysis was classified into 5 categories from no seizures to developmental and epileptic encephalopathy; GEFS+ is generally considered benign but includes severe spectrum disorders (pqac-00000018, pqac-00000015, pqac-00000004) | (pqac-00000018, pqac-00000015, pqac-00000004) |
| Developmental / behavioral features | GEFS+ classically often does not affect development, but mild intellectual impairment can occur in some affected individuals; severe spectrum disorders overlapping with GEFS+ may include developmental and epileptic encephalopathies. | HP:0001249 Intellectual disability; HP:0001263 Global developmental delay | Most affected subjects in one classic report had normal or superior intellect except one mildly intellectually impaired proband; no GEFS+-wide developmental prevalence estimate retrieved (pqac-00000017, pqac-00000019, pqac-00000015) | (pqac-00000017, pqac-00000019, pqac-00000015) |


*Table: This table summarizes the supported GEFS+ phenotypic spectrum, onset/remission timing, and available frequencies from classic and recent evidence. It is useful for mapping clinical features to HPO terms and capturing temporal disease characteristics for a knowledge base.*