Rare diseases · Sign or symptom
Clonus
HP:0002169
What it means
A series of rhythmic and involuntary muscle contractions (at a frequency of about 5 to 7 Hz) that occur in response to an abruptly applied and sustained stretch.
Clonus is a manifestation of spasticity that can occur with lesions of the corticospinal tract. Only sustained clonus (5 beats or more) is considered abnormal.
Rare diseases that can present with this33
Very common80–99%
4Common30–79%
13- Alpha-N-acetylgalactosaminidase deficiency
- Autosomal dominant spastic paraplegia type 12
- Autosomal dominant spastic paraplegia type 19
- Autosomal dominant spastic paraplegia type 42
- Autosomal recessive spastic paraplegia type 59
- Autosomal spastic paraplegia type 58
- Hyperornithinemia-hyperammonemia-homocitrullinuria syndrome
- Leukoencephalopathy with bilateral anterior temporal lobe cysts
- Mutilating hereditary sensory neuropathy with spastic paraplegia
- Oculocerebrorenal syndrome of Lowe
- Primary progressive freezing gait
- PRUNE1-related neurological syndrome
- Self-limited neonatal epilepsy
Sometimes5–29%
16- 6-pyruvoyl-tetrahydropterin synthase deficiency
- Adult-onset autosomal dominant leukodystrophy
- Autosomal dominant spastic paraplegia type 29
- Autosomal dominant spastic paraplegia type 37
- Autosomal dominant spastic paraplegia type 8
- Autosomal recessive spastic paraplegia type 62
- Congenital muscular dystrophy with cerebellar involvement
- Distal deletion 10q syndrome
and 8 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: Involuntary rhythmic muscular contractions and relaxations
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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.