What is SMA and why is genetic testing critical?
Spinal Muscular Atrophy, or SMA, has been in the news recently. It’s a rare genetic condition that can only be confirmed by a genetic test.
What is SMA?
Spinal Muscular Atrophy is a severe and progressive neuromuscular disorder which is caused by genetic mutations or deletions to the SMN1 gene.
There are several different types of SMA, and everyone is affected differently. The most common type is 5q SMA which includes SMA Types 1,2, 3 and 4. Symptoms are often seen in children from an early age when they appear to be ‘floppy’ with muscle weakness. They can have difficulty sitting up and crawling and often find breathing or swallowing a challenge.
Type 1 SMA is typically seen in children at a very early age and without treatment they are unlikely to live beyond two years of age. However, symptoms are seen at later stages of a child’s development in type 2, type 3 and type 4. Type 4 SMA might start in people over 18 for example.
What causes SMA?
SMA is a recessive disorder, which means that most children with SMA have inherited an SMN1 gene mistake from both of their parents. Parents of children with SMA are usually completely healthy – this is because although they usually have a mistake in one copy of their SMN1 gene, their second SMN1 gene is normal.
If both parents have an SMN1 gene mistake, there’s a:
- 1 in 4 (25%) chance their child will have SMA
- 2 in 4 (50%) chance their child will carry the altered gene, but will not have SMA
- 1 in 4 (25%) chance their child will not carry the altered gene or have SMA
Genetic testing is needed to diagnose SMA
Genetic testing is available on the NHS to detect changes to the SMN1 gene. This test is undertaken for anyone living in the South East of England, by the South East Genomic Medicine Service.
SMA is a progressive condition meaning it gets worse over time, so it is crucial that testing is completed as quickly as possible.
Testing is freely available on the NHS via the NHS Genomic Medicine Service with no charge to the referring Trust. Results will be returned to the clinician within 14 days.
New rapid SMA test now available
Based on feedback from clinicians, our scientists in the South East NHS Genomic Medicine Service have developed a new rapid test that can diagnose SMA within three days.
It is not currently available on the NHS, but can be ordered directly from our laboratory partner at Synnovis.
Children who have received this rapid test so far have received their results within 24 hours meaning they can start treatment straight away and avoid any further delays.
What treatment is available for SMA?
Treatment for SMA has transformed in recent years. Although there is no cure, there are now several options available that can stop further deterioration.
Clare Galtrey, Consultant Adult Neurologist and SMA expert at St. George’s Hospital adds,
“For many many years a diagnosis of SMA would be devastating for a family. However, that’s all changed. Amazingly, we now have new and remarkable treatments available. Speed is of the essence, so if a child can get a genetic test done quickly then treatment can start almost immediately. These two things combined can transform the future for these children and their families.”
Current treatments can’t reverse symptoms which is why early diagnosis makes a huge difference.
There are currently three main treatment options for SMA:
- Nusinersen targets a specific gene to produce extra amounts of the SMN protein that is known to be lacking in people with SMA.
- Risdiplam targets a specific gene to produce extra amounts of the SMN protein that is known to be lacking in people with SMA.
- Zolgensma, a gene therapy only available for patients with Type 1 SMA. It’s a one off treatment that delivers a working copy of the SMN1 gene into the patient, which enables the body to replace the faulty gene.
There is a wealth of information about treatment options on the SMA UK website.
