Rare diseases · Sign or symptom
Generalized myoclonic seizure
HP:0002123
What it means
A generalized myoclonic seizure is a type of generalized motor seizure characterized by bilateral, sudden, brief (<100 ms) involuntary single or multiple contraction of muscles or muscle groups of variable topography (axial, proximal limb, distal). Myoclonus is less regularly repetitive and less sustained than is clonus.
Rare diseases that can present with this66
Very common80–99%
8- Carnosinase deficiency
- Early infantile developmental and epileptic encephalopathy
- MERRF
- Myoclonic epilepsy of infancy
- Paternal uniparental disomy of chromosome 6 syndrome
- Pontocerebellar hypoplasia type 2
- Seizures-intellectual disability due to hydroxylysinuria syndrome
- X-linked neurodegenerative syndrome, Bertini type
Common30–79%
28- Alacrimia-choreoathetosis-liver dysfunction syndrome
- Combined immunodeficiency with facio-oculo-skeletal anomalies
- Combined oxidative phosphorylation defect type 27
- Congenital muscular dystrophy with intellectual disability and severe epilepsy
- Dravet syndrome
- Early-onset spastic ataxia-myoclonic epilepsy-neuropathy syndrome
- Epilepsy with eyelid myoclonia
- Epilepsy with myoclonic-atonic seizures
- Gaucher disease
- Gaucher disease type 2
- Gaucher disease type 3
- Glycine encephalopathy
- Intellectual disability-obesity-brain malformations-facial dysmorphism syndrome
- Intellectual disability-seizures-hypophosphatasia-ophthalmic-skeletal anomalies syndrome
- Isolated permanent neonatal diabetes mellitus
- Isolated succinate-CoQ reductase deficiency
- Krabbe disease
- Lafora disease
- Microcephaly-intellectual disability-sensorineural hearing loss-epilepsy-abnormal muscle tone syndrome
- Mitochondrial DNA-associated Leigh syndrome
- Northern epilepsy
- Perioral myoclonia with absences
- Progressive myoclonic epilepsy with dystonia
- Spastic paraplegia-severe developmental delay-epilepsy syndrome
- Spinal muscular atrophy-progressive myoclonic epilepsy syndrome
- Succinic semialdehyde dehydrogenase deficiency
- X-linked intellectual disability-cerebellar hypoplasia syndrome
- Xq12-q13.3 duplication syndrome
Sometimes5–29%
29- 3-phosphoglycerate dehydrogenase deficiency, infantile/juvenile form
- Angelman syndrome
- Atypical Rett syndrome
- Bilateral frontoparietal polymicrogyria
- Bilateral generalized polymicrogyria
- Bilateral polymicrogyria
- Biotinidase deficiency
- DNM1L-related encephalopathy due to mitochondrial and peroxisomal fission defect
and 21 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 epileptic myoclonus · Generalised myoclonic seizure · Generalised myoclonic seizures · Generalized epileptic myoclonus · Generalized myoclonic seizures · Myoclonic epilepsy, progressive · Myoclonus 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.