People with spinal muscular atrophy (SMA) may be at a higher risk for developing other medical conditions, known as comorbidities. More severe types of SMA may lead to the development of more severe complications.

As new SMA treatments become available, these relationships might change, though it remains unclear whether new or future therapies could alter the occurrence of comorbidities. Further research is needed to better understand how SMA interacts with other health conditions.

Disorders of the Muscular and Skeletal Systems

SMA primarily affects muscles, with symptoms such as hypotonia (muscle weakness) leading to complications in the musculoskeletal system.

One common complication is scoliosis, a curvature of the spine. In people with SMA, the muscles are too weak to hold the spine in the correct alignment, and gravity slowly pulls the curve of the spine into an abnormal alignment. Scoliosis is most common in children with SMA type 1 (Werdnig-Hoffmann disease) and type 2, and it also affects people with type 3 (Kugelberg-Welander disease).

About 90 percent of children with SMA develop scoliosis. In children with SMA, scoliosis develops on average between ages 6 and 8, but onset can be as early as 8 or 9 months of age. Age of onset is later in children who continue to be able to walk. Scoliosis may be treated with bracing, surgery, or an implanted vertical expandable prosthetic titanium rib (VEPTR) device.

Scoliosis can cause or worsen breathing difficulties, affect sitting balance, and impact arm movement. Other spinal deformities can occur, including kyphosis (a forward curve of the upper spine) and lordosis (an inward curve of the spine).

Additionally, pelvic obliquity (tilting of the pelvis) affects one-third of people with SMA, leading to hip dislocation in some cases. Hip dislocation is less prevalent in people with SMA who continue to stand or walk. Hip surgery is sometimes necessary to alleviate pain or improve balance.

Children with SMA may also develop joint contractures, where joints become stiff due to limited movement. Splints, braces, and physical therapy or occupational therapy may help prevent joint contractures.

Some children with SMA type 2 may experience limited movement in the jaw (temporomandibular joint), which affects mouth opening. Speech therapy can help improve jaw movement.

Respiratory Complications

In individuals with SMA types 1 and 2, weak intercostal muscles (the muscles between the ribs) combined with a relatively stronger diaphragm may lead to a bell-shaped chest and pectus excavatum (a sunken chest). Scoliosis can also contribute to changes in the chest shape, further complicating breathing. These changes, along with muscle weakness, can cause chronic respiratory failure, which may become life-threatening without intervention.

People with SMA frequently experience respiratory infections due to weakened respiratory muscles and difficulty coughing effectively. These infections, if untreated, can progress rapidly and lead to serious complications like pneumonia.

Treatments for respiratory complications include:

• Noninvasive breathing support, such as bilevel positive airway pressure (BiPAP) or continuous positive airway pressure (CPAP) machines
• Invasive breathing support, such as tracheostomy or mechanical ventilation
• Respiratory therapy
• Devices like a VEPTR device to help with chest expansion

Cardiovascular Conditions

Apart from complications related to the muscles and skeleton, abnormalities of the cardiovascular system (heart and blood vessels) are some of the most frequently reported comorbidities in people with SMA.

Some researchers believe that the genetic mutation (variation) in the SMN1 gene, which causes SMA, might also influence heart function. Individuals with SMA type 1 are more likely to have structural heart abnormalities, such as issues with heart valves or septal walls (the walls separating the heart chambers). Arrhythmias (irregular heart rhythms) can occur in people with SMA types 1, 2, and 3.

Managing Related Conditions To Improve Quality of Life

There are effective ways to manage many of the complications associated with spinal muscular atrophy. Treating these conditions can help people with the condition maintain function, comfort, and a higher quality of life.

If you or your child starts showing signs of a complication, it’s important to reach out to your health care team for guidance and treatment options as early as possible.

Talk With Others Who Understand

On mySMAteam, the social network for people with spinal muscular atrophy and their loved ones, more than 2,600 members come together to ask questions, give advice, and share their stories with others who understand life with spinal muscular atrophy.

Have you or a loved one developed complications from SMA? Share your experience in the comments below, or start a conversation by posting on your Activities page.