Spinal Muscular Atrophy (SMA)

SMA, or Spinal Muscular Atrophy, is a genetic disorder that affects the muscles used for movement. It is caused by a mutation in the SMN1 gene, which produces a protein necessary for the survival of motor neurons. Without this protein, motor neurons in the spinal cord degenerate, leading to muscle weakness and atrophy.

SMA symptoms

The symptoms of SMA vary depending on the type and severity of the condition. Common symptoms include muscle weakness, difficulty with movement, respiratory problems, and difficulty swallowing.

Individuals with SMA may also have a curved spine, or scoliosis, and may experience muscle wasting.

SMA Types

• Spinal Muscular Atrophy Type 1 (SMA1):

Also known as Werdnig-Hoffmann disease, is the most severe form and usually appears in the first few months of life.

• Spinal Muscular Atrophy Type 2 (SMA2):

Typically appears in infancy or early childhood. Children suffering from this type can usually sit, but have difficulty swallowing and breathing because of their muscle's weakness.

• Spinal Muscular Atrophy Type 3 (SMA3):

Type 3 is a milder form of SMA that typically appears in early childhood or adolescence. Individuals with Type 3 SMA typically have more muscle strength than those with Type 1 or Type 2 SMA, but may experience muscle weakness, difficulty with movement, and fatigue.

• Spinal Muscular Atrophy Type 4 (SMA4):

SMA Type 4, also known as adult-onset SMA or proximal spinal muscular atrophy, is the rarest form of SMA and typically appears in adulthood. Symptoms of Type 4 SMA may include muscle weakness and atrophy, difficulty with movement, and respiratory problems. The progression of symptoms in Type 4 SMA is typically slower than in other forms of the condition, and individuals with Type 4 SMA may be able to maintain mobility and function for many years.

SMA inheritance

SMA is an inherited condition and is passed down in an autosomal recessive manner, meaning that an individual must inherit two copies of the mutated SMN1 gene - one from each parent - to develop the condition. If an individual inherits only one copy of the mutated gene, they are considered a carrier and will not typically develop symptoms of the condition.