Sma Disease

SMA Disease: An In-Depth Exploration

What is SMA Disease?

Spinal muscular atrophy (SMA) is a genetic disorder that affects the motor neurons, which are nerve cells that send signals from the brain and spinal cord to the muscles. In SMA, these motor neurons are damaged or missing, causing progressive muscle weakness and atrophy.

Types of SMA Disease

There are four main types of SMA, classified based on the age of onset and severity of symptoms:

• Type 1: Infantile SMA - Most severe type, with symptoms beginning in the first few months of life and leading to severe muscle weakness and respiratory difficulties.
• Type 2: Intermediate SMA - Symptoms appear between 6 and 18 months of age, causing moderate muscle weakness and difficulties with walking and standing.
• Type 3: Juvenile SMA - Mildest type, with symptoms appearing between 2 and 17 years of age, resulting in mild to moderate muscle weakness, primarily in the legs and arms.
• Type 4: Adult-Onset SMA - Rarest type, with symptoms developing in adulthood, causing slowly progressive muscle weakness and fatigue.

Causes of SMA Disease

SMA is caused by mutations in the SMN1 gene, which provides instructions for making the survival motor neuron protein (SMN). This protein is essential for the maintenance and function of motor neurons.

Most cases of SMA are inherited in an autosomal recessive pattern, meaning that both parents must carry the mutated gene for the child to inherit the disease.

Symptoms of SMA Disease

Symptoms of SMA vary depending on the type, but common symptoms include:

• Muscle weakness and atrophy, especially in the legs and arms
• Difficulty breathing, swallowing, and speaking
• Scoliosis (curvature of the spine)
• Skeletal deformities

Diagnosis and Treatment of SMA Disease

SMA is diagnosed through genetic testing to identify the mutated SMN1 gene.

There is currently no cure for SMA, but treatments focus on symptom management and preventing complications. These treatments include:

• Nusinersen (Spinraza) - An FDA-approved medication that provides a functional copy of the SMN gene
• Risdiplam (Evrysdi) - An oral medication that increases SMN protein production
• Onasemnogene abeparvovec-xioi (Zolgensma) - A one-time gene therapy that replaces the mutated SMN1 gene with a functional copy
• Physical therapy, occupational therapy, and speech therapy - To improve muscle strength, mobility, and communication