1 in 40
people in the UK are thought to carry the gene change that causes SMA
Understanding SMA
What is spinal muscular atrophy?
Spinal Muscular Atrophy (SMA) is a genetic condition that affects the nerve cells in the spinal cord, so messages from the brain struggle to reach the muscles. Muscles that are not used become weak and waste away, which is called atrophy.
1 in 4
chance of a child being affected when both parents are carriers
1 in 20,000
babies are affected by type 1 SMA
1 million
people in the UK are estimated to be carriers
How SMA affects the body
SMA damages nerve cells in an area of the spinal cord called the anterior horn. Those nerves carry messages from the brain to the muscles. When they are damaged, the link is broken: the muscles do not receive the signal to move, so they cannot be used and begin to waste away.
This can lead to problems with breathing as well as everyday movement such as crawling, walking, feeding and holding up the head. The severity of symptoms depends on the type of SMA a person has.
Common effects
- Muscle weakness that can affect crawling, walking and head control
- Difficulties with feeding and swallowing
- Breathing problems, which can be the most serious part of the condition
- Weakness that gets worse over time as muscles waste (atrophy)
Everyone’s experience is different. Always speak to your clinical team about your own or your child’s care.
How SMA is inherited
Types 1, 2 and 3 are autosomal recessive conditions. That means a child is affected only when both parents carry the gene change. If both parents are carriers, there is a 1 in 4 chance of a child having SMA, a 2 in 4 chance of a child being a carrier, and a 1 in 4 chance of neither.
SMA does not discriminate between gender or race. Most carriers have no idea they carry the gene change, because being a carrier does not cause symptoms.
Types, treatment and research
SMA is grouped into types depending on when symptoms start and how severe they are. Type 1 is the most severe form and affects babies in their first year. Types 2 and 3 usually appear later and can be milder, although everyone is affected differently.
For many years there was no treatment and no cure. Treatments now exist, including nusinersen (Spinraza), which increases the protein that SMA affects. Research continues, and we fund research into the causes and treatment of SMA so that more families have options.
Read more about treatments and SpinrazaWhy newborn screening matters
More help and support
Visit TreatSMA for the bigger picture
TreatSMA is a volunteer led UK charity with detailed, up to date information on living with SMA. If you want to understand the condition further, find community groups, or get help with wellbeing and benefits, their website is the place to start.
We are proud to work alongside other organisations in the SMA community. Whatever you are facing, you do not have to work it out alone.
Visit TreatSMATreatSMA is a separate charity. Their site also has information on treatments, newborn screening, news and a business directory.
Community groups
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