Rare diseases · Sign or symptom
Fasciculations
Muscle twitch
HP:0002380
What it means
Fasciculations are observed as small, local, involuntary muscle contractions (twitching) visible under the skin. Fasciculations result from increased irritability of an axon (which in turn is often a manifestation of disease of a motor neuron). This leads to sporadic discharges of all the muscle fibers controlled by the axon in isolation from other motor units.
This finding can be visible clinically and can be demonstrated by electromyography (EMG).
Rare diseases that can present with this39
Very common80–99%
3Common30–79%
17- Adult-onset autosomal recessive cerebellar ataxia
- Adult-onset distal myopathy due to VCP mutation
- Amyotrophic lateral sclerosis
- Autosomal dominant adult-onset proximal spinal muscular atrophy
- Autosomal recessive ataxia, Beauce type
- Autosomal recessive axonal Charcot-Marie-Tooth disease due to copper metabolism defect
- Autosomal recessive cerebellar ataxia-movement disorder syndrome
- Hyperkalemic periodic paralysis
- Isaacs syndrome
- Lower motor neuron syndrome with late-adult onset
- Multifocal motor neuropathy
- Neutral lipid storage disease with myopathy
- O'Sullivan-McLeod syndrome
- Pontocerebellar hypoplasia type 7
- Spinocerebellar ataxia type 2
- Spinocerebellar ataxia type 36
- Tay-Sachs disease
Sometimes5–29%
18- African trypanosomiasis
- Autosomal dominant Charcot-Marie-Tooth disease type 2Z
- Behavioral variant of frontotemporal dementia
- Benign Samaritan congenital myopathy
- Charcot-Marie-Tooth disease type 1F
- Crimean-Congo hemorrhagic fever
- Early-onset progressive diffuse brain atrophy-microcephaly-muscle weakness-optic atrophy syndrome
- Frontotemporal dementia with motor neuron disease
and 10 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, and Orphanet separately records 3 diseases where this sign is specifically absent. A sign on this page is a conversation to have with a clinician, not a conclusion.
Part of the broader category
Also called: Fasciculation · Muscle fasciculation
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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.