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This information is for if you, if you / your child has been recently diagnosed with SMA-LED.

SMA-LED is a rarer form of SMA that begins in infancy or early childhood and progresses slowly. Like 5q SMA, SMA-LED affects the nerve cells called motor neurons. These cells transmit electrical signals from the spinal cord to muscles for voluntary muscle contraction.

SMA-LED causes motor neurons to malfunction, resulting in weakness in leg muscles, which is most severe in the thigh muscles (quadriceps). Children and adults often have a ‘waddling’ or unsteady walk and have difficulty climbing stairs and getting up from sitting.

There is only limited information about SMA-LED because it is so rare, but your or your child’s medical team will be able to discuss how it affects you / your child and how to manage symptoms for maximum comfort and quality of life.

SMA-LED has been linked to mutations in two different genes:

  • DYNC1H11-2: Further information can be found here.
  • BICD23-6: Further information can be found here.
Some of the genes that cause rarer forms of SMA are associated with more than one condition, so please be aware that the provided website links may give information about disorders additional to SMA.

SMA-LED has an Autosomal Dominant inheritance pattern, which means that only one faulty gene copy passed on from a parent with the condition is enough to cause the disease.

To find out more about this, please see our information guide: The Inheritance Patterns of Some Rarer Forms of SMA.

Though not a substitute for professional medical advice, MedlinePlus is a service of the US National Library of Medicine (NLM) and provides more information about SMA-LED here.


Provides information and support for anyone in the UK affected by any form of SMA.


Provides information and support for families with children with a disability.

  1. Harms et al. (2012) Mutations in the tail domain of DYNC1H1 cause dominant spinal muscular atrophy. Neurology 78: 1714-1720.
  2. (last accessed 16th August 2022)
  3. Neveling et al. (2013) Mutations in BICD2, which encodes a golgin and important motor adaptor, cause congenital autosomal-dominant spinal muscular atrophy. Am J Hum Genet 92: 946-954.
  4. Peeters et al. (2013) Molecular defects in the motor adaptor BICD2 cause proximal spinal muscular atrophy with autosomal-dominant inheritance. Am J Hum Genet 92: 955-964.
  5. Oates et al. (2013) Mutations in BICD2 cause dominant congenital spinal muscular atrophy and hereditary spastic paraplegia. Am J Hum Genet 92: 965-973.
  6. (last accessed 16th August 2022)

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Author: SMA UK Information Production Team
Last updated: August 2022
Next full review due: August 2024

Links last checked: September 2023

The information provided in this guide, on our website, and through links to other websites, is designed to complement not be a substitute for clinical and professional care and advice.

For more detail about how we produce our information, please see these pages.

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