Spinal muscular atrophy is a group of inherited diseases that cause progressive muscle degeneration and weakness, eventually leading to death.
Causes, incidence, and risk factors
Spinal muscular atrophy (SMA) is a collection of different muscle diseases. Grouped together, it is the second leading cause of neuromuscular disease. Most of the time, a person must get the defective gene from both parents to be affected. Approximately 4 out of every 100,000 people have the condition.
The most severe form is SMA type I, also called Werdnig-Hoffman disease. Infants with SMA type II have less severe symptoms during early infancy, but they become progressively weaker with time. SMA type III is the least severe form of the disease.
Rarely, SMA may begin in adulthood. This is usually a milder form of the disease.
A family history of spinal muscular atrophy is a risk factor for all types of the disorder.