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Start free with EleplanProximal spinal muscular atrophy type 4
ORPHA:83420Clinical subtype
Also called SMA type 4 · SMA type IV · SMA-IV · SMA4 · Spinal muscular atrophy, adult form
What it is
A rare genetic motor neuron disorder characterized by degeneration of alpha motor neurons in the spinal cord and lower brainstem. Proximal spinal muscular atrophy (SMA) type 4 is a rare subtype which manifests after 18 years of age with mild proximal muscle weakness.
Key facts
- Age of onset
- Adult
- Inheritance
- Autosomal recessive
- Classified as
- Clinical subtype
Recorded for the broader condition
- Prevalence
- 1-9 / 100 000 (annual incidence, Europe)Proximal spinal muscular atrophy
Orphanet records these for the broader condition rather than for this specific form. They are a starting point, not a figure for this subtype — subtypes often differ, and some are defined by being rarer than the condition they sit under.
Genes
1 modifying gene — variants that can change how the disease behaves, not cause it
ICD-10 codes
ICD-10 has no distinct code for most rare diseases, so many are filed under the nearest available one. A shared code identifies the group, not this disease — the ORPHAcode above is what identifies it.
Related health topics
Reached through the ICD-10 categories this disease is filed under, so these describe the broader group rather than this disease specifically.
Benefit programs to look at
Programs whose eligibility touches the same ICD-10 categories. Eligibility is decided by the administering agency, never by this page.
Cross-references
Orphadata Science: Free access data from Orphanet. © INSERM 1999. Data version 2026-06-23. Available under CC BY 4.0. This is a reference, not medical advice.
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