What Is Spinal Muscular Atrophy (SMA)?

Is your child showing signs of motor delays? If so, this could be an early warning sign of a serious medical condition known as spinal muscular atrophy (SMA), a rare neuromuscular disease that causes the muscles to become weak and waste away. Approximately 10,000 to 25,000 children and adults have spinal muscular atrophy in the U.S., and around 1 in every 50 Americans is a genetic carrier. There is no complete cure for SMA, and since August is Spinal Muscular Atrophy Awareness Month, we hope to bring awareness to this condition, so more research can be done to find a cure.

What Is Spinal Muscular Atrophy? neuron in the colors blue and orange

SMA is a rare genetic disease that affects approximately 1 in 10,000 children in the United States, and is the number one genetic cause of infant mortality. People with SMA are either missing a part of the Survival Motor Neuron 1 (SMN1) gene or have a mutated gene; having this defective gene means that they do not produce enough survival motor neuron (SMN) protein, which is vital for the health of nerve cells in the spinal cord that control muscle movement. If these nerve cells are not functioning, the muscles do not receive the signals that tell the muscles to contract, which causes the muscles to atrophy, or become smaller and weaker. The condition mainly affects the muscles closest to the torso and neck, and the muscle weakness will generally worsen with age. 

The 5 Types Of Spinal Muscular Atrophy

There are 5 types of spinal muscular atrophy:

  • Type 0– This is very rare and very serious, and can be detected before birth, usually because of decreased fetal movement in the weeks prior to delivery. After birth, babies will have weak muscle tone and weak respiratory muscles, which makes it hard for them to breathe and eat. Infants with this form of SMA might only survive a few months.
  • Type 1– Also referred to as Werdnig-Hoffman disease, this type of SMA accounts for around 60% of cases. It is a severe form of muscle weakness that is evident before 6 months of age; infants with this form of the disease have limited movement, cannot sit without support, and have trouble eating and breathing. Most children with type 1 will die before age 2. 
  • Type 2– Also referred to as Dubowitz disease, this type of SMA is usually diagnosed after 6 months of age, but before age 2. Children can sit without support, but cannot walk or stand without aid. Most children with type 2 SMA will live into adulthood. 
  • Type 3– Also referred to as Kugelber-Welander disease, this type causes muscle weakness that begins after early childhood. Type 3 can also be diagnosed in the teenage years, and those who suffer from it will be able to walk, but will have limited mobility as they grow, and will need a wheelchair. Life expectancy is normal. 
  • Type 4– This is a rare adult form of SMA, accounting for less than 1% of all diagnosed cases. It does not appear until the mid-30s, and will lead to mild motor impairment. Most people with this type of the disease have a normal life expectancy.

How SMA Is Diagnosed

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One way SMA can be diagnosed is by an electromyography.

If a doctor suspects SMA, usually after observing weakness or a delay in reaching developmental milestones, they will perform a blood test to look for mutations of the SMN1 gene. The blood work can identify 95% of SMA types 1, 2, 3, and 4, and can show if someone is a carrier of the gene, meaning that they can pass the condition on to their children. If the blood work shows that the gene is normal, but there is a family history of the genetic mutation, other tests can be done, including:

  • Electromyography– records electrical activity of the muscles during rest and contraction
  • Nerve conduction velocity study– measures the nerves’ ability to send electrical signals
  • Other blood tests performed by a neurologist

If SMA is suspected at birth, a small blood sample will be taken and screened for genetic conditions; if the test is positive for SMA, follow-up testing will be done to confirm the gene. 

Treatment For Spinal Muscular Atrophy

There is no complete cure for spinal muscular atrophy, but if you or your child is diagnosed with the disease, the earlier you seek treatment, the better. The treatment depends on the type of SMA and the symptoms, but can range anywhere from occupational therapy to medical equipment such as braces, crutches, walkers, and wheelchairs. There is now also a prescription medication available to treat SMA: in December 2016, the U.S. Food and Drug Administration (FDA) approved Nusinersen (Spinraza™),  the first drug to receive approval to treat children and adults with SMA. The drug is an injection that goes into the fluid surrounding the spinal cord, which helps increase the production of the SMN protein. 

Research to find a cure for SMA is ongoing, and, in 2019, the FDA approved a gene therapy for children under 2 years of age. This gene replacement therapy, known by the brand name Zolgensma, is a one-time infusion that delivers a functional copy of the defective or missing gene to affected cells.

Spinal muscular atrophy, while rare, is one of the more common rare diseases according to the SMA Foundation; it can occur in any child, especially if the gene runs in your family. If you’re concerned, you can get tested to find out if you carry the gene, and your baby will get tested when born, as well. If your baby does have the gene, more testing will be done to get a proper diagnosis. child sitting on a stone row with crutches leaning on the stone row next to child.

Treatments and therapies for children and adults with SMA have come a long way, and there is hope: many people living with the condition can live a long life with therapy. Having a good health insurance plan can help reduce the out-of-pocket costs for the testing and therapy required for illnesses like SMA; if your current plan is not sufficient, and you would like to compare plans to find the most coverage with the most savings, EZ can help. Our agents will compare all plans in your area and find the right plan for you and your family’s needs. To get free instant quotes, simply enter your zip code in the bar above, or to speak to a local licensed agent, call 888-350-1890.