What is it?

Spinal muscular atrophy (SMA) is a genetic neuromuscular disease that causes muscles to weaken and waste. People with SMA lose a specific type of nerve cell in the spinal cord that controls muscle movement (called motor neurons). Without these motor neurons, muscles don’t receive neural signals that cause the muscles to move. Certain muscles become smaller and weaker due to lack of use. The muscle weakness usually worsens with age.
There are different types of SMA that are caused by different changes in the same genes. The types differ in the age of onset and in the severity of muscle weakness. The age at which SMA symptoms begin roughly correlates with the severity: The earlier the age of onset, the greater the impact on motor function.

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Signs & symptoms

SMA symptoms range from mild to severe, depending on the type.
SMA is a progressive disease - the muscles weakness worsens with age and there is deterioration in muscle control, movement, and strength.
The weakness tends to be more severe in the muscles that are close to the center of the body (proximal) compared to muscles away from the body's center (distal).
Bone and joint problems, such as spinal curvatures, can develop if the back muscles are weakened.
Swallowing problems and breathing difficulties can occur if the muscles used for these functions are affected.
Sensory, mental, and emotional functioning is entirely normal in people with SMA.


The diagnosis of SMA is based on medical history, physical examination, and one or more of these tests:
- Blood tests can check for high levels of creatine kinase. Deteriorating muscles release this enzyme into the bloodstream.
- Genetic test for identifies problems with the SMN1 gene.
- Nerve conduction test: An electromyogram (EMG) measures the electrical activity of nerves muscles and nerves.
- Rarely, a physician may perform a muscle biopsy. A biopsy can show atrophy or loss of muscle.


SMA cannot be cured at this time. Currently, the treatment for SMA is for managing and supporting the symptoms, such as physical and occupational therapy and assistive devices, like orthopedic braces, crutches, walkers, and wheelchairs.
Today, there is more treatment that can help for some of the patients:
- Disease-modifying therapy - a drug that stimulates the production of SMN protein (the protein that is absent in SMA and caused the disease).
- Gene replacement therapy - This therapy replaces a missing or faulty SMN1 gene (the mutated gene in SMA) with a functioning gene. This therapy is for children younger than two years old.

☝️ This is not a substitute for professional medical advice. Please consult with your physician before making any medical decision.

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