Spinal muscular atrophy (SMA) is a rare neuromuscular disorder that gradually loses muscle movement and strength. It happens due to a mutation in the SMN1 gene, which encodes a protein essential for the maintenance and function of motor neurons. SMA symptoms include muscle weakness and wasting, respiratory difficulties, and problems with swallowing and eating. There is no cure, but SMA treatment is available to manage symptoms and improve quality of life.
As mentioned above, spinal muscular atrophy happens due to a mutation in the SMN1 gene. This gene provides instructions for making a protein called survival motor neuron (SMN). This protein is essential for maintaining and functioning motor neurons, which are nerve cells that control muscle movement. The SMN1 gene is missing or defective in people with SMA, so little or no SMN protein gets produced. Losing this protein causes motor neurons to die, leading to muscle weakness and wasting.
Several types of SMA disease get classified according to the age at which symptoms first appear and the severity of muscle involvement. The most common form, type I SMA (also known as Werdnig-Hoffmann disease), typically occurs in infants before six months. This form gets characterized by severe muscle weakness, respiratory difficulties, and problems with swallowing and eating.
Type II SMA (also known as intermediate SMA) generally begins between 7 and 18 months of age. People with type II SMA have less severe muscle weakness than those with type I, and they can often sit without support. Type III SMA (also known as Kugelberg-Welander disease) usually begins after 18 months. People with type III SMA can stand and walk, but they may eventually lose the ability to walk due to progressive muscle weakness.
One of the most common SMA symptoms is muscle weakness, which typically begins in the arms and legs and spreads to the trunk. As SMA progresses, muscles waste away (atrophy), and people lose the ability to move their limbs. This loss of movement can lead to problems with swallowing and eating and respiratory difficulties.
In infants with SMA type I, muscle weakness is so severe that they cannot sit without support or hold their heads up. They may also have difficulty breathing and feeding and may need assistance with basic daily activities such as bathing and dressing. People with SMA type II generally have less severe muscle weakness than those with type I. They are often able to sit without support but may eventually lose the ability to walk due to progressive muscle weakness. People with SMA type III generally have milder muscle weakness than those with type II. They may eventually lose the ability to walk but can often stand and maintain their balance.
There is no cure for SMA disease, but treatment is available to manage symptoms and improve quality of life. SMA treatment typically involves a multidisciplinary approach that includes physical therapy, occupational therapy, respiratory care, and nutritional support. Physical therapy can help prevent joint contractures and maintain range of motion. Occupational therapy can help people with SMA develop skills for daily living and learn how to use adaptive equipment. Respiratory care can help prevent lung infections and improve breathing. Nutritional support is essential for people with SMA to maintain a healthy weight and get the necessary nutrients.
SMA is a rare disease, and there is no one-size-fits-all approach to treatment. The best SMA treatment plan will depend on the individual needs and symptoms. A person should talk to their doctor about what treatments are right for them.
There is no known way to prevent SMA. However, early diagnosis and treatment are essential for managing symptoms and improving quality of life. If a person or their child has symptoms of SMA, they should talk to their doctor as soon as possible.