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Proximal spinal muscular atrophy type 1

Disease definition

A rare, genetic proximal spinal muscular atrophy characterized by degeneration of alpha motor neurons in the anterior horns of the spinal cord and lower brain stem manifesting with onset of severe and progressive muscle weakness in the first 6 months of life and presenting with severe, generalized hypotonia and weakness,. Dysphagia and respiratory impairment may also be present at presentation or appear at a later stage. Classically, before the advent of recent therapies, type 1 patients never achieved sitting without support.


Classification level: Subtype of disorder
  • Synonym(s):
    • Infantile spinal muscular atrophy
    • Infantile-onset spinal muscular atrophy
    • SMA type 1
    • SMA type I
    • SMA-I
    • SMA1
    • Werdnig-Hoffmann disease
  • Prevalence: 1-9 / 100 000
  • Inheritance: Autosomal recessive 
  • Age of onset: Infancy, Neonatal
  • ICD-10: G12.0
  • ICD-11: 8B61.0
  • OMIM: 253300
  • UMLS: C0043116
  • MeSH: -
  • GARD: 7883
  • MedDRA: -

Detailed information

General public


Disease review articles


Clinical Outcome Assessment (COA)

  • Patient-Centered Outcome Measures (PCOMs)
  • English (2023) - PROQOLIDTM

Genetic Testing

ERN produced/endorsed by ERN(s)   FSMR produced/endorsed by FSMR(s)
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