Frequently Asked Questions (FAQs) About Spinal Muscular Atrophy
Whether you are living with spinal muscular atrophy (SMA) or a caregiver for someone with SMA, here is a guide to the basics of SMA.
What is spinal muscular atrophy?
Spinal muscular atrophy (SMA) is a genetic disorder where muscles become weak and waste away. It happens when spinal cord nerve cells die, causing important muscles to become inactive.1,2
What causes spinal muscular atrophy?
SMA is a genetic disorder that is inherited by children from their parents and is present at birth. It is caused by mutations in a gene called SMN1. This gene is important for the survival of brain cells that communicate with muscles.3
All types of SMA are inherited in a “recessive” pattern, meaning that both copies of the SMN1 gene must be mutated to have SMA. We inherit 2 copies of all of our genes, 1 from each parent. People with SMA inherit 1 mutated copy of SMN1 from each parent.3
Read more about the causes of SMA.
What are the different types?
The 4 major types of SMA are caused by an altered SMN1 gene. Because this gene is on chromosome 5q, these types are called “5q SMAs.”4
Type 1
This is the most common type of SMA, usually appearing within the first 6 months of life. It accounts for about half of all SMA cases. It is also known as Werdnig-Hoffmann disease.5-7
Type 2
This is also called Dubowitz disease. About 20 percent of all SMA cases are type 2. Symptoms usually appear between 7 and 18 months old.4,5,7
Type 3
This is also called Kugelberg-Welander disease. About 30 percent of all SMA cases are type 3. Symptoms usually appear between 18 months old and adulthood.4-6
Type 4
This is an adult form of SMA. It accounts for less than 5 percent of all SMA cases. Symptoms appear during adulthood, usually after 30 years old.4-6
Read more about the types of SMA.
What are the symptoms?
Symptoms of SMA vary based on the type of SMA. The most common symptoms are muscle weakness and low muscle tone. People with the same type of SMA can have different experiences. Read more about the different symptoms of SMA and how they vary by type.
How is SMA diagnosed? What tests can I expect?
SMA can be diagnosed using a genetic test. Genetic tests use a blood sample to identify alterations in a certain gene, and testing is usually done after symptoms appear.
Early diagnosis is important because of new treatments that are more effective when started early. Read more about genetic testing, screening, and physical exams.
Can SMA be cured?
There is no cure for SMA. However, new treatment options can help to improve outcomes.
What are the treatment options for this condition?
Treatment for SMA generally combines supportive therapy with disease-modifying drugs. Supportive therapy focuses on nutrition and breathing support, improving mobility, and preventing complications of muscle weakness.
Three disease-modifying drugs have been approved for people with SMA:8
Read more about different treatment options for SMA.
How can I best support my child with SMA?
Talking to a child about SMA can be challenging. Caregiving is also usually a full-time responsibility that can impact other areas of your life. Find support and information in our caregiver corner.
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