SMA with Lower Extremity Predominance (SMA-LED)

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

What is SMA - LED?

This rarer form of SMA begins in infancy or early childhood and progresses slowly. Children have weakness in their leg muscle weakness which is most severe in their thigh muscles (quadriceps). Children and adults often have a ‘waddling’ or unsteady walk and have difficulty getting up from sitting and climbing stairs.

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

Which gene is affected?

Some of the genes that cause rarer forms of SMA are associated with more than one condition, so please be aware that the website links suggested might provide information that is not just about SMA.

The affected gene is:

  • DYNC1H11

Further information can be found here.

Inheritance pattern

SMA-LED has an Autosomal Dominant inheritance pattern.

To find out more about this please see our information sheet ‘The inheritance patterns of some rarer forms of SMA’.

Support and resources

Though not a substitute for professional medical advice, the US National Library of Medicine, Genetics Home Reference provides more information which you can find here.

Phone: 01789 267520

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

Phone: 0808 808 3555
Provides information and support for families with children with a disability

Version: 1.1
Author: SMA UK Information Production Team
Published: August 2018
Last updated: March 2019

Next full review due August 2021


1. Harms et al. (2012) ‘Mutations in the tail domain of DYNC1H1 cause dominant spinal muscular atrophy’, Neurology, 78, pp. 1714-1720.


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