Types of spinal muscular atrophy (SMA)

Because some people can have more copies of the SMN2 backup gene and others can have fewer, there is a wide range of severity in individuals affected by SMA.

Download the Facts About SMA guide

Types of spinal muscular atrophy (SMA)

Because some people can have more copies of the SMN2 backup gene and others can have fewer, there is a wide range of severity in individuals affected by SMA.

Download the Facts About SMA guide

Severity of SMA

There are 4 main types of SMA (Types 1-4) that range in severity and when symptoms first appear. It can be fatal in some people and less severe in others. SMA Type 1 is the most common and is very serious. The fifth, and most severe, form of SMA is Type 0.

SMA has a wide range of severity
The natural history of SMA chart showing the percentage of children who were alive and free of permanent breathing support: 8.1 months old (75%), 10.5 months old (50%), 13.6 months old (25%), and 24 months old (8%)

SMA Type 1 is the most common form of SMA and affects about 6 out of every 10 children with SMA. Most children with SMA Type 1 have 2 copies of the SMN2 backup gene. In some cases, children may have more than 2 copies or fewer than 2 copies. SMA Type 1 is a life-threatening condition that needs immediate attention. SMA Type 1 can quickly lead to the need for breathing and eating support, and without treatment is likely to be fatal within the first 2 years of life. SMA Type 1 is very severe, but signs and symptoms may vary at first—which means caregivers may not see them right away. Knowing what signs and symptoms to look for is critical in getting a diagnosis and starting a treatment.


Children with SMA Type 2 commonly have 3 copies of the SMN2 backup gene and show symptoms between 6 and 18 months of age. Typically, they are not able to walk or stand without support and have a shortened life span.


Symptoms begin after 18 months of age, usually in early childhood. Children with SMA Type 3 usually have 3 or 4 copies of the SMN2 backup gene. As they grow, these children may lose their ability to walk and other muscle functions.


This is a very rare form of SMA. Adults with SMA Type 4 usually have 4 copies or more of the SMN2 backup gene. Symptoms of SMA Type 4 can start around 18 years of age but typically don’t begin until after age 20 or 30 years. People with SMA Type 4 usually only experience mild muscle weakness.


This is the most severe form of SMA and affects a baby that is still in the womb. SMA Type 0 can be fatal before birth and is almost always fatal within the first year of life.


See the signs and symptoms of SMA

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SMA Type 1 is the most common and is life threatening

Only 8% of children in the natural history* of SMA Type 1 were alive and free of continuous breathing support at 24 months old. Continuous breathing support means that children needed a machine to help them breathe for at least 16 hours per day for 2 weeks or more.

A chart displaying the range of severity in people affected by SMA

*Natural history refers to the progression of a disease in a person over time without treatment.

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Does my child have SMA?

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Important Safety Information

What is the most important information I should know about ZOLGENSMA?

  • ZOLGENSMA can cause acute serious liver injury. Liver enzymes could become elevated and may reflect acute serious liver injury in children who receive ZOLGENSMA.
  • Patients will receive an oral corticosteroid before and after infusion with ZOLGENSMA and will undergo regular blood tests to monitor liver function.

Important Safety Information

What is the most important information I should know about ZOLGENSMA?

  • ZOLGENSMA can cause acute serious liver injury. Liver enzymes could become elevated and may reflect acute serious liver injury in children who receive ZOLGENSMA.
  • Patients will receive an oral corticosteroid before and after infusion with ZOLGENSMA and will undergo regular blood tests to monitor liver function.
  • Contact the patient’s doctor immediately if the patient’s skin and/or whites of the eyes appear yellowish, or if the patient misses a dose of the corticosteroid or vomits it up.

What should I watch for before and after infusion with ZOLGENSMA?

  • Viral respiratory infections before or after ZOLGENSMA infusion can lead to more serious complications. Contact the patient’s doctor immediately if you see signs of a possible viral respiratory infection such as coughing, wheezing, sneezing, runny nose, sore throat, or fever.
  • Decreased platelet counts could occur following infusion with ZOLGENSMA. Seek immediate medical attention if a patient experiences unexpected bleeding or bruising.

What do I need to know about vaccinations and ZOLGENSMA?

  • Talk with the patient’s doctor to decide if adjustments to the vaccination schedule are needed to accommodate treatment with a corticosteroid.
  • Protection against respiratory syncytial virus (RSV) is recommended.

Do I need to take precautions with the patient’s bodily waste?
Temporarily, small amounts of ZOLGENSMA may be found in the patient’s stool. Use good hand hygiene when coming into direct contact with bodily waste for 1 month after infusion with ZOLGENSMA. Disposable diapers should be sealed in disposable trash bags and thrown out with regular trash.

What are the possible or likely side effects of ZOLGENSMA?
The most common side effects that occurred in patients treated with ZOLGENSMA were elevated liver enzymes and vomiting.

Indication

What is ZOLGENSMA?
ZOLGENSMA is a prescription gene therapy used to treat children less than 2 years old with spinal muscular atrophy (SMA). ZOLGENSMA is given as a one-time infusion into the vein. ZOLGENSMA was not evaluated in patients with advanced SMA.

The safety information provided here is not comprehensive. Talk to the patient’s doctor about any side effects that bother the patient or that don’t go away.

You are encouraged to report suspected side effects by contacting the FDA at 1-800-FDA-1088 or www.fda.gov/medwatch, or AveXis at 833-828-3947.

Please see the Full Prescribing Information.

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