What is SMA?

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Spinal Muscular Atrophy (SMA) is the number one genetic killer of infants. And yet, so many folks haven’t heard of this disease. Florence was diagnosed with type 1 SMA at 4 months. She couldn’t bear weight on her legs or move her arms very much. The movement she did have, she lost slowly or quickly over time. Every child is different. Some type 1 children are a lot stronger, others are a lot weaker.

SMA affects every muscle. Children with SMA type 1 never reach basic milestones such as sitting up, crawling or walking. It is similar to ALS, in that the muscles atrophy over time. It is a deeply painful process for the parents to watch their child weaken over time and succumb to a disease that has no approved treatment. There is currently no approved treatment to reverse this process, so type 1 children struggle to reach their 1st or 2nd birthdays. But this is changing. 

SMA is a hereditary disease, meaning most of the time, both parents need to be carries of this genetic mutation. If they are, there is a 1 in 4 chance their children will be affected with SMA.

In the spine, there is a particular gene (SMN1) that produces a particular type of protein. That protein is essential to the healthy development of motor neurons, which people need in order to do many things: breathe, swallow, walk, run.

In SMA patients, the SMN1 gene is defunct and either doesn’t produce the necessary proteins at all or doesn’t produce enough of them. So the motor neurons are weak or die off, leaving the body’s muscles to atrophy without use.

From CURESMA.org:

“There are four primary types of SMA: type I, II, III, and IV. The type of SMA is based on age of onset and the highest physical milestones achieved.

No two people with SMA have identical experiences. Even among those with the same type, the progression of the disease can differ. Decisions about care and treatment should be made according to each individual’s needs.

SMA Type I

Type I—the most severe and the most common—is usually diagnosed during an infant’s first six months. Babies with SMA type I face many physical challenges, including muscle weakness and trouble breathing, coughing, and swallowing. They may need breathing assistance or a feeding tube. Type I is often fatal early on in life. 60% of all SMA cases are type I.

SMA type I is also know as Werdnig-Hoffmann disease.


Type II is usually diagnosed after six month of age, but before two years of age. The first sign is often a delay in meeting motor milestones, or failing to meet milestones entirely.

Individuals affected by SMA type II can typically sit up without help, though they may need assistance getting into a seated position, but they are unable to walk and will require a wheelchair.


Type III is usually diagnosed after 18 months of age, but before three years of age. However, SMA type III can be diagnosed as late as the teenage years. Individuals affected by SMA type III are initially able to walk, but have increasingly limited mobility as they grow and eventually, many need to use a wheelchair.

Type III is also called Kugelberg-Welander disease or juvenile SMA.


SMA type IV is very rare. It usually surfaces in adulthood, and it leads to mild motor impairment.  While symptoms can begin as early as age 18, they usually begin after age 35.


Every family has the right to receive support. They have the right to ask questions. They have the right to refuse or request certain treatments, or to change their mind. They have the right to make decisions in accordance with their own values and priorities.”

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