SMA with Progressive Myoclonic Epilepsy (SMA-PME)
This information is for if your child has been recently diagnosed with SMA - LED.
What is SMA - PME?
This rare form of SMA is a neurological condition that causes weakness and wasting (atrophy) of muscles and a combination of seizures and uncontrollable muscle jerks (myoclonic epilepsy). This is caused by a loss of the motor neuron nerve cells in the spinal cord and in both the brain stem which connects the spinal cord to the brain.
There’s limited information about SMA-PME because it’s so rare, but your child’s medical team will be able to discuss how it will affect your child and how to manage symptoms for maximum comfort and quality of life.
What are the symptoms and effects?
After a few years of typical development, children with SMA-PME begin to have weakness and wasting (atrophy) in the muscles in their lower limbs. This causes difficulty walking and frequent falls. The muscles in their upper limbs are affected later, and soon the muscle weakness and atrophy spreads throughout their body. Once weakness reaches their muscles used for breathing and swallowing, it leads to life-threatening breathing problems and an increased risk of pneumonia.
A few years after the muscle weakness begins, children start to experience recurrent seizures (epilepsy). Most people with SMA-PME have a variety of types of seizure which often increase in frequency over time and are not usually well-controlled with medication. Individuals with SMA-PME may also have episodes of rhythmic shaking (tremors), usually in their hands; these tremors are not thought to be related to epilepsy.
Some people with SMA-PME develop hearing loss caused by nerve damage in their inner ear.
For children with SMA-PME, life expectancy is usually into late childhood or early adulthood. Sadly, life is often shortened by respiratory failure or pneumonia.
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:
- ASAH11 - Further information can be found here.
SMA-PME has an Autosomal Recessive inheritance pattern.
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.
Together for Short Lives
Phone: 0808 8088 100
Provides information, support and services for families of children who are expected to have short lives.
Author: SMA UK Information Production Team
Published: September 2018
Last updated: March 2019
Next full review due September 2021
1. Zhou et al. (2012) ‘Spinal muscular atrophy associated with progressive myoclonic epilepsy is caused by mutations in ASAH1’, American Journal of Human Genetics, 91, pp. 5–14.
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