Rare diseases · Sign or symptom
Generalized tonic seizure
HP:0010818
What it means
A generalized tonic seizure is a type of generalized motor seizure characterized by bilateral limb stiffening or elevation, often with neck stiffening without a subsequent clonic phase. The tonic activity can be a sustained abnormal posture, either in extension or flexion, sometimes accompanied by tremor of the extremities.
Characterized by a sudden increase in muscle tone whereby the body, arms, or legs make sudden stiffening movements and consciousness is usually preserved. Tonic seizures can occur during sleep. Tonic seizures usually affect both sides of the body, and cause a fall if the affected person was standing when the seizure started.
Rare diseases that can present with this24
Common30–79%
10- COG2-CDG
- Early-onset epileptic encephalopathy-cortical blindness-intellectual disability-facial dysmorphism syndrome
- Early-onset progressive diffuse brain atrophy-microcephaly-muscle weakness-optic atrophy syndrome
- Hyperekplexia-epilepsy syndrome
- Intellectual disability-seizures-hypophosphatasia-ophthalmic-skeletal anomalies syndrome
- Lennox-Gastaut syndrome
- PCDH19 clustering epilepsy
- Self-limited infantile epilepsy
- Self-limited neonatal epilepsy
- Unilateral polymicrogyria
Sometimes5–29%
10- Bilateral generalized polymicrogyria
- Distal deletion 12q syndrome
- DPM1-CDG
- Early infantile developmental and epileptic encephalopathy
- Early-onset epileptic encephalopathy and intellectual disability due to GRIN2A mutation
- Lissencephaly due to LIS1 mutation
- PURA-related severe neonatal hypotonia-seizures-encephalopathy syndrome
- Rasmussen syndrome
and 2 more in this range
The range is how often this sign appears among people diagnosed with each disease — it is not a probability of having any of them. Many of these signs also occur in common, non-rare conditions. A sign on this page is a conversation to have with a clinician, not a conclusion.
Part of the broader category
Also called: Generalised hypertonic seizure · Generalised tonic seizure · Generalised tonic seizures · Generalized hypertonic seizure · Generalized tonic seizures · Hypertonic seizures
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Start free with EleplanThis page uses the Human Phenotype Ontology (2026-06-23) — Human Phenotype Ontology Consortium, hpo.jax.org. Disease associations from Orphanet (INSERM), CC BY 4.0. Content is educational and is not medical advice.