Spinal muscular atrophy


What is Spinal Muscular Atrophy?

Spinal muscular atrophy (SMA) is a disorder that degrades the central nervous system, caused by a mutation in the survival motor neuron (SMN) on the 5th chromosome. The mutation causes muscles to not receive signals from the nerve cell located in the spinal cord that controls voluntary muscle movement. This ultimately leads to your body continuously becoming weaker, which may result in a decrease in daily activities such as breathing, swallowing, eating, and walking.

SMA has five subtypes from 0 to 4 based on the age at the onset of symptoms. SMA type 0, which is rare, begins prior to birth and is the most severe. SMA type 1 is the most common type, with symptoms typically appearing before 6 months of age. Onset of SMA type 2 is often between 3 and 15 months of age and less severe than type 1. SMA type 3 has a more varied age of onset, ranging between 18 months and adulthood. Type 4 SMA is a rare, mild form of SMA, which may be diagnosed in late adolescence or adulthood.

How common is Spinal Muscular Atrophy?

SMA affects approximately 1 in 11,000 births in the U.S., and about 1 in every 50 Americans is a genetic carrier.1 A pan-ethnic study in 2012 found that carrier frequency in North America was highest in white individuals (1 in 47) and lowest in Hispanic individuals (1 in 68) and Black individuals (1 in 72).2

Questions regarding your Spinal Muscular Atrophy therapy?

You can reach the Accredo Spinal Muscular Atrophy care team between 8am to 11pm Monday through Friday and Saturday 8am to 5pm Eastern Standard Time.

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  • 1About Spinal muscular atrophy (SMA). Cure SMA. Accessed 9/15/2023. About SMA
  • 2Mercuri E, Sumner CJ, Muntoni F, Darras BT, Finkel RS. Spinal muscular atrophy. Nat Rev Dis Primers. 2022 Aug 4;8(1):52. doi: 10.1038/s41572-022-00380-8. PMID: 35927425


What are the symptoms of Spinal Muscular Atrophy?1, 2

SMA symptoms can vary from mild to severe based on subtype. The primary symptom of SMA is muscle weakness, which can lead to a person needing assistance with daily tasks such as cleaning, walking, eating, and driving. The muscles that are most affected are those closest to the center of the body. These muscles include those of the shoulders, hips, thighs, and upper back. The lower limbs seem to be affected more than the upper limbs, and deep tendon reflexes are decreased. Other symptoms can include gastrointestinal symptoms, such as gastroesophageal reflux and poor bowel motility or constipation.

How is Spinal Muscular Atrophy diagnosed?2

Newborn screening for SMA is being implemented throughout the United States and is currently conducted in 48 states. If the patient is already born, SMA should be suspected in any infant with unexplained weakness or hypotonia. To diagnose SMA, genetic testing is utilized to detect mutations in the SMN1 gene.

Carrier testing for SMA is also available using a molecular genetic test to identify the most common SMN1 mutation associated with SMA.

  • 1Mercuri E, Sumner CJ, Muntoni F, Darras BT, Finkel RS. Spinal muscular atrophy. Nat Rev Dis Primers. 2022 Aug 4;8(1):52. doi: 10.1038/s41572-022-00380-8. PMID: 35927425.
  • 2a2bSpinal muscular atrophy (SMA) - diseases. Muscular Dystrophy Association. Accessed 9/15/2023. <a href="https://www.mda.org/disease/spinal-muscular-atrophy" target="_blank">Muscular Dystrophy Association</a>


Spinal Muscular Atrophy

The following specialty medications are available at Accredo, a specialty pharmacy for Spinal Muscular Atrophy

Medication Manufacturer
Evrysdi™ (risdiplam) Genentech USA, Inc.
Spinraza™ (nusinersen) Biogen, Inc.
Zolgensma® (onasemnogene) Novartis Pharmaceuticals Corp.

Financing Your Care

Financial assistance coordination may be available to help with your medication costs, including manufacturer and community programs. Accredo representatives are available to help find a program that may work for you.

MedicationFinancial assistance program contact information
The Assistance Fund

Financial Guidance

Life-saving specialty medication can be expensive. Learn how the Accredo teams help individuals find ways to afford the medication they need to survive in this video.

Find Support

There are many organizations that support research and advocacy for Spinal Muscular Atrophy. See below for a few of those organizations.

Spinal Muscular Atrophy Organizations

Government Organizations

Meet the Team

Accredo’s Spinal Muscular Atrophy care team is dedicated to serving you and we understand the complexity of your condition. Our specialty-trained clinicians are available from 8am to 11pm Monday through Friday and Saturday 8am to 5pm Eastern Standard Time, to answer any questions. You can reach the Spinal Muscular Atrophy dedicated care team at


Why We Do It

Accredo supports patients with chronic and complex conditions and helps them live their best life. Watch our video to learn why we do what we do for our patients.

Why We Do It video transcript

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