spinal muscular atrophy, type III
Findings
No curated finding names spinal muscular atrophy, type III yet. Everything below is reference data from Mondo, HPO and GenCC, not evidence about what affects it.
Definition
Proximal spinal muscular atrophy type 3 (SMA3) is a relatively mild form of proximal spinal muscular atrophy characterized by muscle weakness and hypotonia resulting from the degeneration and loss of the lower motor neurons in the spinal cord and the brain stem nuclei.
Definition from the Mondo Disease Ontology (MONDO:0009672), read 2026-09-29. CC BY 4.0.
- Inheritance
- Autosomal recessive inheritance
- Onset and course
- Juvenile onset · Progressive · Early young adult onset
HPO, annotations 2026-09-02
Features
14 features
What the disease is reported to present with, and how often among people who have it — never how often a feature means the disease. HPO, annotations 2026-09-02.
- Absent Achilles reflexHPOHP:0003438
- 2 of 2 reported patients
- Absent patellar reflexesHPOHP:0006844
- 2 of 2 reported patients
- EMG: chronic denervation signsHPOHP:0003444
- 2 of 2 reported patients
- Lower limb muscle weaknessHPOHP:0007340
- 2 of 2 reported patients
- Pelvic girdle amyotrophyHPOHP:0008946
- 2 of 2 reported patients
- Pelvic girdle muscle weaknessHPOHP:0003749
- 2 of 2 reported patients
- Proximal lower limb amyotrophyHPO
Show the remaining 2
- Shoulder girdle muscle atrophyHPOHP:0003724
- 1 of 2 reported patients
- Spinal muscular atrophyHPOHP:0007269
Genes
2 genes
Germline variants in the gene encoding each protein, as classified by GenCC submitters, each in their own words. Limited, disputed and refuted submissions are listed too.
- SMN1; SMN2HGNC:11117
- Strong · Genomics England PanelApp · Autosomal recessive · 2021
- Supportive · Orphanet · Autosomal recessive · 2021
- SMN1; SMN2HGNC:11118
- Moderate · PanelApp Australia · Autosomal recessive · 2025
Where it sits
- A kind of
Other names
11 names
Resolves to: spinal muscular atrophy, type III
- Also called
- Kugelberg Welander SyndromeKugelberg-Welander diseaseSMA type 3SMA type IIISMA-IIISMA3spinal muscular atrophy IIIspinal muscular atrophy type 3spinal muscular atrophy-3spinal muscular atrophy, familialspinal muscular atrophy, type III, modifier of