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5 Things You Should Know About Spinal Muscular Atrophy

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The way you’re able to move any part of your body often comes down to muscles — everything from mobility to digestion, blood circulation and breathing. If you have a condition that leads to issues in these soft tissues, it can have a big impact on your day-to day life. One such condition is spinal muscular atrophy.

Spinal muscular atrophy (SMA) is a group of rare hereditary conditions that can range from moderate muscle-related issues to a shortened life expectancy. In many patients, SMA can cause muscle weakness, motor development issues and muscle “wasting” (atrophy) over time. There are five types of spinal muscular atrophy, each of which may affect you differently.

There is no cure for any form of spinal muscular atrophy, and treatment is based on symptom management. While some forms of spinal muscular atrophy can decrease life expectancy, research and treatment options have improved in recent years. Two medications — nusinersen and Zolgensma — both received FDA approval for SMA in the past five years.

While spinal muscular atrophy can be a debilitating disease, advocates with the condition have outlined how it’s possible to live a full life. Mighty contributor Precious Feliciano, a woman with SMA type 2, shared about her experience:

Growing up with a neurological disorder, spinal muscular atrophy type II, has never been easy. I have never, nor will I ever be able to crawl, stand, or walk, for my muscles are weaker than the “norm,” and will progress as I get older. Though at times my illness has come in the way of me completing my goals, I have never let it stop me from eventually achieving those goals.

For those interested in learning more, here are five things you should know about spinal muscular atrophy:

1. Spinal muscular atrophy is one of the most common rare diseases.

Spinal muscular atrophy is one of the more common rare diseases, affecting approximately 1 in 6,000 to 1 in 10,000 people. There are four main types of SMA, which typically correlate with the age you develop symptoms, plus a prenatal version of the condition.

  • Type 0. Also known as prenatal SMA, symptoms of the disease may be present when the baby is still in the womb or at birth.
  • Type 1. Known as Werdnig-Hoffman disease or infantile-onset, SMA symptoms show up between birth and 6 months old.
  • Type 2. Known as the immediate form of SMA, the disease often appears between the ages of 6 months to 1 year old.
  • Type 3. Also known as Kugelberg-Welander disease, people often develop symptoms between age 1 and 3 years old, but sometimes as late as the teen years.
  • Type 4. Usually the mildest form of the condition and the most rare, people with SMA type 4 can develop symptoms as early as 18-21 years old, but it’s more common after the age of 30.

The severity of symptoms and prognosis differs depending on what type of SMA you have. SMA type 0 and 1 are most often fatal, especially without treatment.

2. The symptoms of spinal muscular atrophy vary by type.

As many people with a rare disease know, symptoms play a major role in helping a doctor diagnosis your condition correctly. What is complicated with spinal muscular atrophy (SMA) is that the symptoms can be very different, ranging from mild to life-threatening, depending on what type of SMA you have.

According to the National Organization for Rare Disorders, SMA type 0 and type 1 are characterized by the most severe symptoms. Type 0 is identified by decreased fetal movement in the womb, joint differences, difficulty swallowing and respiratory failure. Type 1 is characterized by severe muscle weakness, lack of motor development and problems swallowing. Patients with SMA type 0 and 1 often do not live past age 2, but new treatment options may improve their life expectancy.

Patients with SMA type 2 will likely take longer to reach motor development milestones and may be able to sit without support, but could require mobility aids for assistance. Life expectancy can vary and is often reduced, but many people with SMA type 2 live into their 20s and 30s, according to the National Library of Medicine. Treatment and clinical care can help the motor development of patients with SMA type 2.

Patients with SMA type 3 and 4 generally have milder symptoms than the other types of SMA. In type 3, symptoms may include scoliosis, respiratory issues and bone fractures, and patients are expected to have a normal lifespan. In type 4, patients may have mild to moderate muscle weakness and other symptoms while their mobility may be slightly impacted.

3. Blood tests are often used to diagnose spinal muscular atrophy.

SMA is caused by changes in your survival motor neuron 1 (SMN1) gene, which are important in the development of your motor neurons. The severity or type of SMA you have is determined by changes to your SMN2 gene. SMA is a autosomal recessive genetic disease, which means that you must inherit two copies of the defective gene (one from each parent) to develop the condition.

Because of its genetic origin, blood tests are often used to diagnose spinal muscular atrophy. According to the National Institute of Neurological Disorders and Strokes, these blood tests can identify at least 95% of SMA types 1, 2 and 3, and could also identify if a person is a carrier of the genes that cause SMA. In some cases, doctors may order muscle biopsies or use nerve conduction velocity tests to diagnose SMA.

When testing to see if you have SMA, doctors may also test for diseases with symptoms that overlap with SMA. This includes other neuromuscular diseases such as Duchenne muscular dystrophy and Charcot-Marie-Tooth disease.

4. Treatment for SMA consists of symptom management.

Treatment for spinal muscular atrophy revolves around treating and managing your symptoms, regardless of your type. Standard therapies for SMA include treating any lung or breathing issues, managing nutrition, and treating scoliosis and hip displacements. Physical therapy, occupational therapy and rehabilitation can also help improve posture, prevent joint immobility and strengthen muscles.

There are two specific therapies approved by the U.S. Food and Drug Administration (FDA) to specifically treat SMA. In 2016, the FDA approved nusinersen, also known as Spinraza, to treat children and adults with SMA. When started early, research suggests this drug helps the prognosis of infants and children with SMA.

In 2019, the FDA approved Zolgensma, a gene therapy for children under the age of 2. Clinical data suggested that a one-time infusion of Zolgensma can change the course of SMA and improve the quality of life for patients. However, at the time of its approval, the cost of a one-time infusion was $2.1 million without insurance or government subsidized help.

5. Most patients with spinal muscular atrophy also develop scoliosis.

Scoliosis — when your spine curves sideways — is a common symptom of SMA. Just like with most symptoms, the severity of scoliosis often corresponds with your SMA type. Most people with SMA types 1 and 2 develop scoliosis, and 50% of people with SMA type 3 develop scoliosis.

There are multiple treatment options for scoliosis, which include physical therapy, wearing braces and surgery. Johns Hopkins Medicine found that rod surgery can help SMA patients with scoliosis, but you may have a longer recovery time than people who do not have SMA.


References (click to expand)


Header image via grejak/Getty Images

Originally published: February 28, 2020
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