Spinal Muscular Atrophy (SMA) is a group of rare, genetically inherited neuromuscular conditions. They cause progressive muscle weakness and loss of movement due to muscle atrophy (wasting) in all of the muscles in the body. The more severe forms of SMA can affect the breathing and swallowing muscles.
SMA affects the central nervous system and the peripheral nervous system. Classified as a motor neuron disease, it develops when motor neurons (nerve cells in the spinal cord controlling muscle movement) progressively lose function.