Spinal Muscular Atrophy (SMA) is a group of inherited diseases that cause progressive muscle degeneration and weakness, eventually leading to death.
It is a debilitating disorder that destroys the nerve cells for walking, head and neck control, swallowing and breathing. It primarily affects children and is the main genetic cause of death in infancy.
The most severe form is SMA type I, also called Werdnig-Hoffman disease. Infants with SMA Type I are born with very little muscle tone, weak muscles, and feeding and breathing problems.
Infants with SMA Type II have less severe symptoms during early infancy, but they become progressively weaker with time.
Rarely, SMA may begin in adulthood. This is usually a milder form of the disease.
SMA has a reported carrier frequency of 1 in 60 and approximately 4 out of every 100,000 people are affected by the disorder.