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What is SMA?

SMA (spinal muscular atrophy) is a disease that robs people of physical strength by affecting the motor nerve cells in the spinal cord, taking away the ability to walk, eat, or breathe. It is the number one genetic cause of death for infants.

SMA is caused by a mutation in the survival motor neuron gene 1 (SMN1). In a healthy person, this gene produces a protein that is critical to the function of the nerves that control our muscles. Without it, those nerve cells cannot properly function and eventually die, leading to debilitating and often fatal muscle weakness.

SMA affects approximately 1 in 11,000 babies, and about 1 in every 50 Americans is a genetic carrier. SMA can affect any race or gender.

There are four primary types of SMA—I, II, III, and IV—based on age of onset and highest physical milestone achieved.

Individuals with SMA have difficulty performing the basic functions of life, like breathing and swallowing. However, SMA does not affect a person’s ability to think, learn, and build relationships with others.

There’s great reason for hope. Thanks to the dedication of our community and the ingenuity of our researchers, we now have the first-ever approved treatment that targets the underlying genetics of SMA. But our work is not done. We know what we need to do to develop and deliver effective therapies. And we’re on the verge of further breakthroughs that will continue to change the course of SMA for everyone affected—from infants to adults—and eventually lead to a cure.

Types of SMA

1

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.

2

SMA Type II

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.

3

SMA Type III

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.

4

SMA Type IV

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.