Spinal muscular atrophy (SMA): genetics and classification

Written and reviewed by Dr Ibrahim Imam, Consultant Neurologist. Last reviewed .

Spinal muscular atrophy (SMA): genetics and classification. SMA is caused by mutations or deletions in the SMN1 gene. Fully referenced neurology checklist.

Genetics: SMN1

  • SMA is caused by mutations or deletions in the SMN1 gene
  • The carrier frequency is about 1:35
  • The incidence is 1:6000 births
  • The severity depends on SMN2 copy number
  • SMN 2 is a disease modifying gene: it generates 10-15% of the SMN protein

Genetics: others

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Classical SMA types

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Major SMA variants

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Other SMA variants

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References

  1. Wang CH, Lunn MR. Spinal muscular atrophy: advances in research and consensus on care of patients. Curr Treat Options Neurol 2008; 10:420-428.
  2. Naruse H, Mitsui J, Ishiura H, et al. LRP12 CGG repeat expansions in patients with adult-onset non-5q spinal muscular atrophy. Neurol Genet 2026; 12:e200440.
  3. Ropper AH, Brown RH. Principles of Neurology Eigth edition. McGraw Hill New York 2005 p945.
  4. Amato A, Russell JA. Neuromuscular disorders. McGraw Hill 2008 New York.Chapter 6.
  5. Russman BS. Spinal muscular atrophy: clinical classification and disease heterogeneity. J Child Neurol 2007; 22:946-951.
  6. And 7 more. Subscribe to see the full list

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