Frequently asked questions

1) What is spinal muscular atrophy (SMA)?

SMA is a rare, serious, inherited condition, in which nerves that control muscles (motor neurons) die.1,2 This results in muscles becoming weak and wasting away, with eventual loss of movement and difficulty with functions such as breathing, swallowing, feeding and speaking1,3,4

References
  • 1. ZOLGENSMA (onasemnogene abeparvovec) Patient information leaflet (September 2022).
  • 2. Lin C-W, et al. Pediatr Neurol. 2015;53(4):293–300.
  • 3. Prior TW, et al. NCBI Bookshelf 2019. Available at: https://www.ncbi.nlm.nih.gov/books/NBK1352. Date accessed: November 2022.
  • 4. Wang CH, et al. J Child Neurol. 2007;22(8):1027–49.

2) What is the cause of spinal muscular atrophy (SMA)?

For motor neurons to be able to work properly and survive, the body needs, among other things, a protein called SMN or ‘survival motor neuron’.1,2 Without SMN protein, motor neurons stop working and die, and muscles become weaker with eventual loss of movement and difficulty with functions such as breathing, swallowing, feeding and speaking3−5

In unaffected people, the body is able to produce the SMN protein from genes called SMN genes. There are 2 types of SMN gene, SMN1 and SMN2:1,2,6−8

  • Survival motor neuron 1 (SMN1)

    The SMN1 gene is the primary gene and produces most of the SMN protein that motor neurons need to work properly1,6−8
  • Survival motor neuron 2 (SMN2)

    Although the SMN2 gene also produces SMN protein, it makes several versions of this protein and only small amounts of these work properly (‘functional SMN protein’).6,8,9 The SMN2 gene therefore acts like a ‘back-up’ to support SMN protein production, but is not able to produce sufficient SMN protein on its own6,9

In people with SMA, the SMN1 gene is either faulty (mutated) or completely missing.6,7,10 The SMN2 gene cannot produce enough functional SMN protein to make up for the loss of the SMN1 gene.1,2,6,8 As a result, there is not enough functional SMN protein produced to keep motor neurons healthy and working properly1,2,7,11

Click here for more information about what causes SMA

References

3) What are the different types of spinal muscular atrophy (SMA)?

SMA is a spectrum disease with a range of symptoms that may vary in severity.1−4 There are different types of spinal muscular atrophy ranging from Types 0–4.1–4 The progression of the types changes depending on the age at onset of symptoms, milestones achieved, and symptoms experienced1−4

References
  • 1. Wang CH, et al. J Child Neurol. 2007;22(8):1027–49.
  • 2. Glascock J, et al. J Neuromuscul Dis. 2018;5(2):145–58.
  • 3. Schorling DC, et al. J Neuromuscul Dis. 2020;7:1–13.
  • 4. Prior TW, et al. NCBI Bookshelf 2019. Available at: https://www.ncbi.nlm.nih.gov/books/NBK1352. Date accessed: November 2022.

4) What are the differences between spinal muscular atrophy (SMA) Types 0, 1, 2, 3 and 4?

There are different symptoms that may occur depending on the type of SMA.1–3 If you notice any of the symptoms below, do not hesitate to contact your doctor1–4

SMA Type 0

Age of symptom onset: Birth2

In the most severe form, symptoms usually begin to develop before birth. The child’s movements may slow down during pregnancy5

SMA Type 1

Age of symptom onset: ≤6 months2,6

  • Poor head control1−3,7,8
  • Weak legs and arms1–3,7,8
  • Fast belly breathing1–3,9
  • Difficulty feeding/swallowing1–3
  • Weak cry and cough3,9

Click here for more information about SMA Type 1

SMA Type 2

Age of symptom onset: 6–18 months2,6

  • Struggles to sit unsupported1–3,10
  • Weak legs and arms1–3,11
  • Can’t roll over10,11
  • Slow/lost physical development1–3,10,12
  • Swallowing and coughing difficulties1–3
  • Shaking hands2,3

Click here for more information about SMA Type 2

SMA Type 3

Age of symptom onset: >18 months–teens2,6

People with this form of SMA may have poor balance, and have problems with standing up and walking/climbing stairs3,13

Click here for more information about SMA Type 3

SMA Type 4

Age of symptom onset: >18 years2

In the mildest form, symptoms don’t appear until adulthood. People with this form of SMA typically have mild weakness, without breathing difficulties3,13

References

5) Is spinal muscular atrophy (SMA) genetic?

Yes, as SMA is caused by a faulty (mutated) or missing gene, it is considered a genetic disease and is usually inherited1

A child inherits 2 copies of each gene, one from their mother and one from their father.2 For a child to be born with SMA, they must inherit a faulty gene from both their mother and their father1

If either copy of the gene (from the mother or from the father) is faulty, the other parent’s unaffected gene can make sure enough SMN protein is produced for the motor neurons to work properly.1,2 People who have one unaffected copy of the SMN1 gene and one faulty copy are known as ‘carriers’ and typically do not show any symptoms.1 Most carriers have no idea they carry the faulty gene until they have a child born with SMA3

Click here for more information about the genetics of SMA

References

6) Is spinal muscular atrophy (SMA) dominant or recessive?

SMA is a recessive disorder which typically occurs if a child inherits 2 copies of the faulty or missing survival motor neuron 1 (SMN1) gene, one from their mother and one from their father.1−3 This type of inheritance pattern is referred to as ‘recessive’, and means that, generally, both parents must be carriers for a 25% chance the disease will be inherited3

Click here for more information about the genetics of SMA

References

7) What are spinal muscular atrophy (SMA) symptoms in carriers?

In general, carriers do not experience symptoms of SMA.1 Most carriers are unaware they have the missing or faulty gene until they have a child with spinal muscular atrophy2

References

8) How common is spinal muscular atrophy (SMA)?

SMA is a rare disease, affecting around 1 in 10,000 newborns, and can impact any race or sex.1−4 Around 1 in 50 people are carriers of SMA, although this will vary slightly depending on your geographical location1,5,6

References
  • 1. Armstrong EP, et al. J Med Econ. 2016;19(8):822–6.
  • 2. Ogino S, et al. Eur J Hum Genet. 2004;12:1015–23.
  • 3. Verhaart IEC, et al. Orphanet J Rare Dis. 2017;12:124.
  • 4. Cure SMA (2020). About SMA. Available at: https://www.curesma.org/about-sma/. Date accessed: November 2022.
  • 5. Lin C-W, et al. Pediatr Neurol. 2015;53(4):293–300.
  • 6. Verhaart IEC, et al. Additional file 2: Table S1. Overview carrier frequencies of SMA. Supplementary material to Verhaart IEC, et al. Orphanet J Rare Dis. 2017;12:124. Available at: https://ojrd.biomedcentral.com/articles/10.1186/s13023-017-0671-8. Date accessed: November 2022.

9) Is spinal muscular atrophy (SMA) more common in males or females?

SMA typically affects males and females equally, this is due to the way that the disease is inherited by the child from their parents1,2

Click here for more information about the inheritance of SMA

References
  • 1. Prior TW, et al. NCBI Bookshelf 2019. Available at: https://www.ncbi.nlm.nih.gov/books/NBK1352.
  • 2. Gulani A and Weiler T. Genetics, Autosomal Recessive. 2021 Jan [Updated 2021 May]. In StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2021 Jan.

10) What are the symptoms of spinal muscular atrophy (SMA)?

There are signs of SMA which are important to look out for, although the signs change depending on the age1−3

For babies at birth:2,4

  • In the most severe form, symptoms usually begin to develop before birth. The child’s movements may slow down during pregnancy4

For babies aged 0–6 months:2,5

  • Poor head control1−3,6−8
  • Weak legs/arms1−3,6−8
  • Weak cry and cough1−3,9
  • Difficulty feeding/swallowing1−3,8
  • Fast belly breathing1−3,9

For babies aged 6–18 months:2,5

  • Weak legs and arms1−3,10,11
  • Struggles to sit unsupported1−3,10,12
  • Can’t roll over10−12
  • Slow/lost physical development1−3,10,12,13
  • Swallowing and coughing difficulties1−3,10
  • Shaking hands2,3,10

For children aged 18 months–teens:2,5

  • People with this form of SMA may have poor balance, and have problems with standing up and walking/climbing stairs3,14

For adults aged >18 years:2

  • In the mildest form, symptoms don’t appear until adulthood. People with this form of SMA typically have mild weakness, without breathing difficulties3,14

Even if your baby seems happy and alert, if you feel there may be a problem, please see your doctor for help and information1,6,15,16

Click here for more information about the signs and symptoms

References

11) How does spinal muscular atrophy (SMA) affect the body?

Signals for muscle movement are generated in the brain.1 However, people with SMA have a genetic mutation that causes their lower motor neurons to deteriorate and stop working.1−6 This means that signals in the brain are not carried from the spinal cord to the muscles.1 If the muscles no longer receive signals telling them to move, they can waste away (atrophy) and become increasingly weaker.1,4−6 This leads to difficulty with movement, breathing, feeding and speaking6−8

Click here for more information about the signs and symptoms

References
  • 1. NIH (2020a). MedlinePlus. Trusted health information for you. SMN1 gene. Available at: https://medlineplus.gov/genetics/condition/spinal-muscular-atrophy/. Date accessed: November 2022.
  • 2. Zayia LC and Tadi P. Neuroanatomy, motor neuron. In StatPearls [Internet]. Available at: https://www.ncbi.nlm.nih.gov/books/NBK554616/. Date accessed: November 2022.
  • 3. Govoni A, et al. Mol Neurobiol. 2018;55(8):6307–18.
  • 4. Glascock J, et al. J Neuromuscul Dis. 2018;5(2):145–58.
  • 5. Kolb SJ, et al. Ann Neurol. 2017;82(6):883–91.
  • 6. ZOLGENSMA (onasemnogene abeparvovec) Patient information leaflet (September 2022).
  • 7. Prior TW, et al. NCBI Bookshelf 2019. Available at: https://www.ncbi.nlm.nih.gov/books/NBK1352. Date accessed: November 2022.
  • 8. Wang CH, et al. J Child Neurol. 2007;22(8):1027–49.

12) Can you cure spinal muscular atrophy (SMA)?

There are currently no cures for SMA.1 However, there are treatments available that can change disease outcomes for patients.2,3 Speak to your doctor for more information about patient care4

References
  • 1. Spinal Muscular Atrophy UK (2021). Drug Treatments & Screening – What’s Happening Now?. Available at: https://smauk.org.uk/drug-treatments-screening-whats-happening-now. Date accessed: November 2022.
  • 2. Schorling DC, et al. J Neuromuscul Dis. 2020;7:1–13.
  • 3. Kirschner J, et al. Eur J Paediatr Neurol. 2020 ;28:38–43.
  • 4. Glascock J, et al. J Neuromuscul Dis. 2018;5(2):145–58.

13) Is there a treatment for spinal muscular atrophy (SMA)?

Yes, there are medications available to treat SMA.1–4 Speak to your doctor for more information about treatment options and patient care1−4

References
  • 1. Glascock J, et al. J Neuromuscul Dis. 2018;5(2):145–58.
  • 2. Novartis Gene Therapies (2022). ZOLGENSMA (onasemnogene abeparvovec) Summary of Product Characteristics.
  • 3. Roche (2021). EVRYSDI (risdiplam) Summary of Product Characteristics.
  • 4. Biogen (2021). SPINRAZA (nusinersen) Summary of Product Characteristics.

14) Who treats spinal muscular atrophy (SMA)?

Your doctor will be your first line of contact when treating SMA. They will refer you to any relevant specialists, such as a pediatric neurologist, and offer you information and advice1,2

References
  • 1. Glascock J, et al. J Neuromuscul Dis. 2018;5(2):145–58.
  • 2. Mercuri E, et al. Neuromuscul Disord. 2018;28(2):103–15.

15) How do you test for spinal muscular atrophy (SMA)?

A genetic blood test is used to confirm a diagnosis of SMA in your child.1,2 Additionally, it can also be used to test if both parents are a carrier of the faulty gene, which will help determine if there is a risk of having a child with SMA2

References

16) Can spinal muscular atrophy (SMA) be detected during pregnancy?

Yes, there are tests available that can be carried out during pregnancy if there is a risk you could have a child with SMA.1 If the tests results show there is a likelihood of you having a child with SMA, you should speak to your doctor for further information and advice1

Reference

17) Can spinal muscular atrophy (SMA) be fatal?

Early diagnosis and treatment are extremely important in SMA to give your child the best chance in life1,2

References
  • 1. Glascock J, et al. J Neuromuscul Dis. 2018;5(2):145–58.
  • 2. Govoni A, et al. Mol Neurobiol. 2018;55(8):6307–18.

18) Can spinal muscular atrophy (SMA) affect adults?

Yes, SMA Type 4 can affect adults over 18 years old.1,2 This is the mildest form of SMA as symptoms don’t appear until adulthood1,2

References
  • 1. Wang CH, et al. J Child Neurol. 2007;22(8):1027–49.
  • 2. Schorling DC, et al. J Neuromuscul Dis. 2020;7:1–13.

19) What are the symptoms of spinal muscular atrophy (SMA) in adults?

Adults with SMA Type 4 can experience mild weakness, without breathing difficulties1

Reference
  • 1. Wang CH, et al. J Child Neurol. 2007;22(8):1027–49.