Rare diseases · Sign or symptom
Severe muscular hypotonia
Severely decreased muscle tone
HP:0006829
What it means
A severe degree of muscular hypotonia characterized by markedly reduced muscle tone.
Rare diseases that can present with this19
Very common80–99%
8- Intermediate nemaline myopathy
- Kyphoscoliotic Ehlers-Danlos syndrome due to FKBP22 deficiency
- Multiple congenital anomalies-hypotonia-seizures syndrome
- PEHO syndrome
- Severe X-linked mitochondrial encephalomyopathy
- SLC39A8-CDG
- TBCK-related encephalopathy-severe hypotonia-craniofacial dysmorphism syndrome
- Zellweger syndrome
Common30–79%
4Sometimes5–29%
7- DK1-CDG
- Glutaryl-CoA dehydrogenase deficiency
- Glycogen storage disease due to glycogen branching enzyme deficiency
- Polyhydramnios-megalencephaly-symptomatic epilepsy syndrome
- PURA-related severe neonatal hypotonia-seizures-encephalopathy syndrome due to a point mutation
- Severe neonatal hypotonia-seizures-encephalopathy syndrome due to 5q31.3 microdeletion
- Severe X-linked intellectual disability, Gustavson type
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: Hypotonia, severe
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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.