What Is Spinal Muscular Atrophy (SMA)?
SMA is an inherited, progressive neuromuscular disease

SMA is a disease of
the central nervous

SMA is known as a neuromuscular disease because it originates in the central nervous system (CNS) and affects the motor neurons that power the muscles in the body. Due to the degenerative nature of the disease, people with SMA will experience a decline in muscle strength over time, although the rate and severity can vary among individuals.

SMA is caused by a survival motor neuron (SMN) protein deficiency. 

All individuals have two survival motor neuron genes. These genes, called SMN1 and SMN2, produce survival motor neuron protein, a protein that is critical for proper body movement.

SMN protein is needed for proper communication between motor neurons in the CNS and muscles in the body. Without SMN protein, motor neurons die off, and with no signals from the CNS, muscles get weaker and weaker.

People with SMA are unable to make enough SMN protein because the survival motor neuron 1 (SMN1) gene is mutated or deleted. 

People with SMA rely on SMN2 to make SMN protein, but the SMN2 gene only produces a small amount of full-length protein for every motor neuron.

SMA affects people of
all ages.

Categorized by type and age of onset, SMA causes many physical symptoms that can become increasingly disabling with age. Symptoms vary among the three SMA types and may include progressive muscle weakness and atrophy.

Early-Onset SMA (Type 1)

Age of onset before 6 months

Life expectancy less than 2 years without permanent ventilation and nutritional intervention

Later-Onset SMA (Type 2)

Age of onset 6-18 months

Life span varies depending on severity. Sits independently but not able to walk

Later-Onset SMA (Type 3)

Age of onset older than 18 months

Normal life span. Can stand
and walk independently but may eventually lose this ability over time

SMA is a genetic disease.

SMA is an autosomal recessive genetic disease. This means that someone is at risk of developing SMA if they inherit two mutated or deleted SMN1 genes—one from each parent. “Carriers” will only inherit one faulty gene that they can still pass on to their children, though they may never display any SMA symptoms themselves. About 1 in every 50 Americans is a genetic carrier of SMA and most are unaware until their child shows symptoms. The most accurate way to diagnose SMA or carrier status is through genetic testing. 

SMA is identifiable.

Genetic testing is an important first step in accurately diagnosing rare diseases like SMA. In cases where a family history of SMA exists or individuals present with symptoms of SMA, genetic testing can help to confirm the diagnosis by looking at genetic material to determine if the SMN1 gene is missing or damaged. For family members of those with SMA, it can tell if someone is a carrier of SMA, which means that the person does not have symptoms of the disease, but can pass it on to their children. Some states also have newborn screening for SMA to help identify and plan for treatment before symptoms even develop. Above and beyond this, genetic testing is often required to initiate SMA treatment.

SMA is progressive but treatment options exist.

Due to the variability of symptoms and timing of disease progression in SMA, it is important to always consult with a physician to determine the best SMA treatment approach for each individual.

After diagnosis, people with SMA can count on a host of helpful resources to assist in setting up a comprehensive treatment plan. Aside from regular visits to a primary care physician, people with SMA may also benefit from multidisciplinary care from pulmonologists, neurologists, orthopedists, physical therapists, and occupational therapists.


Increased risk of bleeding complications has been observed after administration of similar medicines. Your healthcare provider should perform blood tests before you start treatment with SPINRAZA and before each dose to monitor for signs of these risks. Seek medical attention if unexpected bleeding occurs.

Increased risk of kidney damage, including potentially fatal acute inflammation of the kidney, has been observed after administration of similar medicines. Your healthcare provider should perform urine testing before you start treatment with SPINRAZA and before each dose to monitor for signs of this risk.

The most common side effects of SPINRAZA include lower respiratory infection, fever, constipation, headache, vomiting, back pain, and post-lumbar puncture syndrome.

These are not all of the possible side effects of SPINRAZA. Call your healthcare provider for medical advice about side effects. You may report side effects to FDA at 1-800-FDA-1088.

Before taking SPINRAZA, tell your healthcare provider if you are pregnant or plan to become pregnant.

Please see full Prescribing Information.

As a courtesy, our full Prescribing Information is also available en Español. For prescribing decisions, please refer to official approved labeling.

This information is not intended to replace discussions with your healthcare provider.


SPINRAZA is a prescription medicine used to treat spinal muscular atrophy (SMA) in pediatric and adult patients.