Rare diseases · Sign or symptom
Focal myoclonic seizure
HP:0011166
What it means
A type of focal motor seizure characterized by sudden, brief (<100 ms) involuntary single or multiple contraction(s) of muscles(s) 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 this9
Common30–79%
3Sometimes5–29%
6- Isolated succinate-CoQ reductase deficiency
- Landau-Kleffner syndrome
- PYCR2-related microcephaly-progressive leukoencephalopathy
- Pyridoxine-dependent-developmental and epileptic encephalopathy
- Skeletal dysplasia-T-cell immunodeficiency-developmental delay syndrome
- Spastic paraplegia-severe developmental delay-epilepsy syndrome
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: Focal myoclonic seizures · Local myoclonic seizures · Localised myoclonic seizure · Localized myoclonic seizure · Partial myoclonic seizure · Partial myoclonic seizures · Segmental myoclonic seizure · Segmental myoclonic 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.