Spinal Muscular Atrophy (SMA) is a genetic disease in which loss of nerve cells in the spinal cord, called motor neurons, affects the part of the nervous system that controls voluntary muscle movement.
There are three types of SMA. SMA type 1 is the most severe and occurs between birth and the age of 6 months. Symptoms include generalized muscle weakness, a weak cry, trouble swallowing as well as sucking, and breathing distress. This type of SMA progresses rapidly and often causes death in early childhood.
SMA type 2 occurs between the age of 6 and 18 months. Weakness is most severe in muscles closest to the center of the body, such as those of the shoulders, hips, thighs and upper back. Respiratory muscles can also be involved. Spinal curvature often develops. This type of SMA is also progressive although progression is slower than in type 1.
SMA type 3 occurs after 18 months of age. Weakness occurs as in type 2 but the disease progresses slowly and walking ability is usually maintained until at least adolescence. Life span is usually not affected.
There is no cure for SMA. However, physiotherapy and other supportive treatments can help muscle strength and chest infections.