Spinal muscular atrophy (SMA) is a condition that causes progressive weakness and wasting (atrophy) in the skeletal muscles, which are used for movement.
Symptoms include low muscle tone, varying degrees of motor delays and impairment, such as not being able to sit independently or walk, as well as breathing and swallowing impairment. There are different types of SMA that range from mild to severe and can be life-limiting. Intelligence is generally unaffected for individuals with SMA.
This condition is caused by pathogenic (disease-causing) variants in the SMN1 gene and exhibits autosomal recessive inheritance. This means that both parents must be carriers to have a 25% chance to have a child with the condition. The risk of being a carrier is based on a person’s ancestry or ethnic background. For example, individuals of Ashkenazi Jewish descent have a 1 in 62 chance to be a carrier.
Carriers typically do not experience any symptoms.