What Is SMA or Spinal Muscular Atrophy

Posted on October 1, 2021

An estimated 1 out of 6 babies are born with Spinal Muscular Atrophy (SMA) in Canada alone, but how much do you really know about SMA?

Spinal Muscular Atrophy is an inherited disease that affects both your nerves and muscles, causing them to become increasingly weak over time. Eventually, SMA causes the loss of the motor neurons that control muscle movement.

SMA does not cause learning difficulties, and children with SMA are bright, sociable, and intelligent. And although SMA has no cure, research continues, and more effective treatments are discovered each day.

If you want to learn more, then you're in the right place. In this guide, you'll learn about the spinal muscular atrophy types, causes, and treatments.

Spinal Muscular Atrophy Type 1

Spinal muscular atrophy type 1 is also referred to as Werdnig-Hoffmann disease and is the most common and most severe type of spinal muscular atrophy. SMA type 1 is an inherited disease that causes weakness noticeable at birth or within the first few months of life.

Babies with SMA type 1 typically can't control their head movements, sit without assistance, and have difficulty feeding. They also have breathing problems due to weakness of the respiratory muscles.

Parents will often notice their babies don't kick with the strength they should, have a smaller chest than usual, and have trouble swallowing their own saliva.

In the past, babies with SMA type 1 rarely lived past the age of 2, but today they live for much longer. Babies with this type of SMA undergo extensive genetic testing to see how many secondary genes they have.

Secondary genes can make at least some of the missing proteins the faulty gene is unable to make. The more copies of this secondary gene a person has, the better their prognosis for SMA type 1 is. New medications and treatments allow children with SMA type 1 to live longer and reach milestones like sitting, standing, and walking.

Spinal Muscular Atrophy Type 2

SMA type 2, also called Dubowitz disease, is most often recorded before 2 years of age, with most cases diagnosed by 15 months. Children with this type of SMA can sit up and support themselves if placed in a sitting position. 

Children with this type of SMA also have difficulty eating enough food to grow and maintain their weight. They also experience weakness in the muscles around the ribcage, which causes children to breathe with their diaphragm muscles.

SMA type 2 also leads to scoliosis, decreased bone density, bone fractures, and a weakened respiratory system. Life expectancy is reduced, but most children make it into young adulthood with proper clinical care.

Spinal Muscular Atrophy Type 3

SMA type 3, also known as Kugelberg-Welander disease, is typically diagnosed after 18 months of age. Children with SMA type 3 can sit and walk independently but show difficulty with prolonged walking, running, climbing stairs, or standing up from a chair.

The leg muscles are mostly affected, along with hand tremors and stiff joints. Often children with SMA type 3 develop joint contractures and scoliosis. They can also still be prone to pneumonia and other respiratory symptoms, but most children with this type live a normal lifespan with treatment. 

SMA Symptoms

In general, SMA affects muscles throughout the body. Sometimes the muscles that control swallowing and breathing are affected, which can cause frequent lung problems such as pneumonia. The most common muscles affected include:

  • Legs
  • Hips
  • Shoulders
  • Back
  • Intercoastal muscles which are between the ribs

The symptoms of SMA vary depending on the type. SMA type 1 is a severe form of SMA and has serious symptoms, including floppy arms and legs, problems swallowing, and inability to support their head without help. Children also have trouble breathing due to weak respiratory muscles and often get enough oxygen during sleep.

SMA type 2 symptoms are usually moderate to severe and involve weakness in the legs, but less so in the arms. Children with this type of SMA can often sit, walk, and stand with some help. They also develop respiratory difficulties and frequent lung infections. SMA Type 2 is also known as chronic infantile SMA.

SMA type 3 is the mildest form, and symptoms are far less severe. Children can typically stand and walk without assistance but have joint stiffness from shortened muscles and tendons and an abnormal muscle tone.  However, children may have difficulty running, climbing stairs, and may a wheelchair to help with mobility later in life.

SMA Causes

SMA is a genetic disease inherited from both parents and caused by a faulty gene called SMN1. If a child has SMA, they inherit two copies of this broken gene, one from each parent. 

Once this happens, the body cannot make the specific protein for the cells that control muscles. And eventually, these cells die, which causes muscle fibers and tissues to waste away. 

If only one copy of this faulty gene is passed along, then a child won't get SMA, but they'll be carriers of the disease and pass this gene on to their children. 

Can SMA Be Prevented?

SMA can't be prevented, and there is no cure, although there are steps you can take to identify your risks if you're thinking of getting pregnant.

If you have a family member with SMA, you're at higher risk of being a carrier. You can get a carrier screening blood test which is a screening done before or during pregnancy.

This screening will tell you if you're at risk of having a baby with SMA, but it can't tell you how severe it would be for the child who might inherit it. The initial results of the screening will determine if further tests are needed. Results can either be:

  • You have two copies of healthy SMN1 genes, and you're at low risk of being a carrier
  • You only have one healthy copy of SMN1, which means the other copy is faulty

Only one parent is tested initially. If you only have one healthy copy of the gene, the second parent is tested. If the second parent is also a carrier, you have a 1 out of 4 chance of having a child with SMA. 

If your partner isn't a carrier, your chances of having a child with SMA are very low. If you find both you and your partner are carriers, you have options such as:

  • Having an amniocentesis test to see if the fetus has SMA
  • Using in vitro fertilization (IVF) and screen for abnormalities
  • Getting pregnant with intrauterine insemination and use a donor 
  • Considering adoption
  • Choosing not to get pregnant

It's best to discuss your results in detail with your doctor and a genetic counselor so you can understand the risks and get advice on what to do next. 

SMA Treatment

There is no cure for SMA, but treatments are available depending on symptoms and SMA type. Children with any type of SMA can benefit from physical therapy, occupational therapy, braces, walkers, and wheelchairs.

To help move air easily through the lungs, children often need a mask or a mouthpiece to use when they sleep at night. Severe breathing problems may require a machine that helps with breathing. 

Since children typically have problems swallowing and not getting the nutrients they need, nutritional therapy is crucial in treating SMA. Children with SMA often have to see a nutritionist or require a feeding tube. A nutritionist will calculate specific nutritional requirements and form a diet plan of healthy foods and nutritional supplements.

Examples of medication therapy for SMA include:

Drugs that work to stimulate the production of SNM protein can often modify the course of the disease. For example, the medication Spinraza is used for children aged 2 to 12 and injected into the spine.

There is also gene therapy available for children under 2 years old. A medication is given once through an IV which helps children have better muscle control and reach milestones like sitting up with no support.

Hope for SMA

While there is no cure for SMA, new and innovative medical treatments allow children to lead longer, healthier, and happier lives. 

It's normal to worry that having a diagnosis like SMA will limit you and your family's ability to get good healthcare coverage that's affordable. SMA is a lifelong journey, and you need to find an insurance company that will stay with you for the long haul.

If you have a child that's newly diagnosed with SMA, then we can help. Insurdinary has a wealth of resources and insurance policies that will help you find the treatments you need. 

Visit us today, get a quote, and check out our blog for tools, tips, and health information.

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