Spinal muscular atrophy (SMA) is a rare genetic condition that causes a decline in muscle strength over time. SMA affects about 1 out of 10,000 people. The condition is classified by type, ranging from type 0 to type 4. Doctors classify SMA type depending on a person’s abilities and when their symptoms began.
“Late-onset SMA” or “adult-onset SMA” usually refers to SMA type 3 (also called Kugelberg-Welander disease) or SMA type 4. These types of SMA start to affect people later in life. For SMA type 3, symptoms begin to appear at any time between 18 months of age through adulthood. For SMA type 4, symptoms generally appear at any time after age 10.
Late-onset SMA affects about 35 percent of people with SMA — SMA type 3 accounts for about 30 percent, and SMA type 4 affects less than 5 percent. Symptom severity can range widely between people with late-onset SMA. Also, the disease can progress slower for some people than others. These differences make outcomes nearly impossible to predict.
Also, new treatments are constantly being developed to slow disease progression. People experiencing SMA today will likely have different experiences than people with SMA years ago. It’s a complex condition, and many factors affecting treatment and symptom progression are changing quickly.
What’s certain is that people with late-onset SMA can lead full lives, start families, and enjoy similar life expectancies as the rest of the population.
Since SMA causes gradual loss of muscle strength, it makes sense that the first signs many people notice are related to muscle weakness: dropping things, falling, and feeling fatigued. Other symptoms can include tremors or twitching of the fingers or tongue. Sometimes, these symptoms can be ignored for years. They may be written off as clumsiness or simply the result of aging.
Children or adults who visit their primary care provider about these symptoms may be referred to a neurologist for further testing and diagnosis. Many neuromuscular disorders have similar symptoms; these include muscular dystrophy, multiple sclerosis, amyotrophic lateral sclerosis, and more. A neurologist may perform tests to measure someone’s fine motor skills or ability to walk for a certain amount of time.
If a neurologist suspects a genetic disorder like SMA, they will usually order genetic testing via a blood test. Genetic testing will provide a definitive diagnosis of SMA.
Researchers only identified the gene that’s responsible for SMA in the 1990s. This means that many people with SMA before then may have been incorrectly diagnosed with other conditions. For example, many people with SMA were instead diagnosed as having muscular dystrophy. Also, late-onset SMA was identified as a condition separate from muscular dystrophy in the 1950s. And the classification types that we now use — SMA type 1, 2, and so on — were not formalized until 1991. Our ability to diagnose SMA has come a long way.
In fact, because of developments in genetic science and genetic testing, newborns are now screened for SMA in most states. Screening is becoming more common because current treatments for SMA can slow disease progression. The earlier treatment starts, the more motor neurons — and physical abilities — can be protected and saved.
Unfortunately, we do not yet have treatments that can reverse motor neuron loss. That means that for older adults, previous levels of ability and mobility cannot necessarily be restored. However, current treatments can still lead to higher quality of life for many people.
For example, while current treatments cannot restore lost motor neurons, some of them can improve how existing motor neurons work. One adult mySMAteam member shared their experience with SMA medication: “I have seen a great increase in my core strength, hand muscles, and thighs. I am riding my tandem bike again with my husband. It has been several small gains over time, but I am so very thankful.”
Medical treatments work best when paired with physical therapy, exercise, and a healthy diet and lifestyle. Your doctor should be able to refer you to a team of specialists that can help you maximize your body’s ability to preserve muscle tone and function.
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Many people with SMA find that making adaptations to their homes or routines can be helpful. For example, some people can begin to find daily chores too tiring. To adapt to this, they can:
People also find adaptive technologies helpful as their symptoms change. Adaptive and assistive technologies can include:
Homes should also be adapted to maximize safety and independence. This means keeping walkways free from clutter, cords, and throw rugs; widening walkways; and choosing hard flooring over carpet when possible. These adjustments can help maximize your independence — and boost your self-esteem and mental well-being.
Adults with SMA can have a variety of life experiences. For many, the condition is not necessarily limiting.
For example, consider this story from one mySMAteam member: “I participated in the Cooper River Bridge Run in Charleston, South Carolina. It is a 10K race, and it was the first time I did it in my wheelchair. My dad and I did it together, along with a friend, and it was a blast! It took a good week of recovery, but I want to do it again next year.”
With technologies and treatments improving rapidly, the future continues to look brighter for those experiencing SMA.
On mySMAteam, the social network for people with SMA and their loved ones, more than 1,400 members come together to ask questions, give advice, and share their stories with others who understand life with SMA.
Were you diagnosed with SMA later in life? Are you thriving with SMA? Share your experience in the comments below, or start a conversation by posting on your Activities page.