Rare diseases · Sign or symptom
Type 1 muscle fiber predominance
HP:0003803
What it means
An abnormal predominance of type I muscle fibers (in general, this feature can only be observed on muscle biopsy).
This finding is demonstrated by muscle biopsy.
Rare diseases that can present with this20
Common30–79%
13- Adult-onset nemaline myopathy
- Amish nemaline myopathy
- Autosomal dominant centronuclear myopathy
- Central core disease
- Childhood-onset nemaline myopathy
- Congenital multicore myopathy with external ophthalmoplegia
- Congenital myopathy with myasthenic-like onset
- Hereditary myopathy with early respiratory failure
- Intermediate nemaline myopathy
- Laing distal myopathy
- Postsynaptic congenital myasthenic syndrome
- Severe congenital nemaline myopathy
- Typical nemaline myopathy
Sometimes5–29%
6The 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: Type 1 muscle fibre predominance · Type I muscle fiber predominance · Type I muscle fibre predominance
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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.