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. Different types of SMA are based on a person’s abilities and when their symptoms began.

“Late-onset SMA” or “adult-onset SMA” usually refers to SMA type 3 or SMA type 4. These forms of SMA start to affect people later in life. Symptoms of SMA type 3 — also called juvenile spinal muscular atrophy or Kugelberg-Welander disease — can begin as early as 18 months old or as late as adulthood. For SMA type 4, symptoms generally appear when you are older than 30.

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. People with late-onset SMA can have a wide variety of symptoms. The disease progresses slower for some people than others. These differences make outcomes nearly impossible to predict.

New treatments are being developed to slow disease progression. People with 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 life expectancies similar to those of the rest of the population.

Late-onset SMA affects about 35 percent of people with SMA.

Here are five facts to know about adult-onset SMA.

1. Early Symptoms May Be Missed

SMA causes gradual loss of muscle strength, so the first signs many people notice are related to muscle weakness. Early signs might include dropping things, falling, and feeling fatigued. Other symptoms, such as tremors or twitching of the fingers, may also occur. 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 ask their healthcare provider about these symptoms may be referred to a neurologist for further testing. To diagnose SMA, other neuromuscular disorders with similar symptoms, such as muscular dystrophy, need to be ruled out. A neurology provider may perform tests, such as electromyography (EMG) or muscle biopsy, to assess your muscles and nerves. Motor function testing may also be used to measure someone’s fine motor skills or ability to walk for a certain amount of time.

2. Genetic Testing Can Diagnose SMA

If a neurologist suspects a genetic disorder like SMA, they will usually order a blood test to check for specific gene mutations (changes). Genetic testing will provide a definitive diagnosis of SMA.

Researchers only identified the gene responsible for SMA in the 1990s. People who developed SMA before that time may have been incorrectly diagnosed with other conditions. For example, many people with SMA were instead diagnosed as having muscular dystrophy. Late-onset SMA was identified as a condition separate from muscular dystrophy in the 1950s. While the classification types we now use — SMA type 1, 2, and so on — were not formalized until 1991.

In fact, all U.S. states now screen newborns for SMA because of developments in genetic science and genetic testing. Screening has become 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.

3. SMA Isn’t Reversible

Unfortunately, there aren’t yet 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.

People with late-onset SMA can lead full lives, start families, and enjoy similar life expectancies as the general population.

For example, although current treatments cannot restore lost motor neurons, some can improve how existing motor neurons work. One mySMAteam member shared their experience with SMA medication: “I’ve seen a great increase in my core strength, hand muscles, and thighs. I’m riding my tandem bike again with my husband. It’s been several small gains over time, but I’m so very thankful.”

Medical treatments work best with physical therapy, exercise, and a healthy diet and lifestyle. Your doctor should be able to refer you to a team of specialists who can help you maximize your body’s ability to preserve muscle tone and function.

4. Adapting Your Home Can Help

Many people with SMA find that making adaptations to their homes or routines can be helpful. For example, some people begin to find daily chores too tiring. To adapt to this, they can:

• Ask for help
• Accept help when it’s offered
• Make deals with friends or family members for less tiring tasks, like knitting or sewing for a neighbor in exchange for cooking or gardening help
• Reorganize the house to move related tasks closer together — like bringing laundry machines in from the garage and moving hampers to the laundry room
• Order items for delivery instead of going shopping

People also find adaptive technologies helpful as their symptoms change. Adaptive and assistive technologies can include:

• Spoons, forks, and cookware that are easier to grip
• Cushions and elevated tray tables to make eating easier
• Elevated toilet seats with handrails
• Shower seats and grab bars in the shower
• Walkers and wheelchairs to use when fatigued

Homes should also be adapted to maximize safety and independence. This means keeping walkways free from clutter, cords, and throw rugs. Widen walkways and choose hard flooring over carpet when possible. These adjustments can help maximize your independence — and boost your self-esteem and mental well-being.

5. You Can Thrive With SMA

Adults with SMA have a variety of life experiences. For many, the condition is not necessarily limiting.

Consider this story from one mySMAteam member: “I participated in 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 looks brighter for people with SMA.

Talk With Others Who Understand

MySMAteam is the social network for people with SMA and their loved ones. On MySMAteam, more than 2,700 members come together to ask questions, give advice, and share their stories with others who understand life with SMA.

Were you diagnosed with adult spinal muscular atrophy? How do the symptoms of SMA affect your daily life? Share your experience in the comments below, or start a conversation by posting on your Activities page.