What is spinal muscular atrophy (SMA)?
Spinal muscular atrophy (SMA) is a genetic (inherited) neuromuscular disease that causes muscles to become weak and waste away. People with SMA lose a specific type of nerve cell in the spinal cord (called motor neurons) that control muscle movement. Without these motor neurons, muscles don’t receive nerve signals that make muscles move. The word atrophy is a medical term that means smaller. With SMA, certain muscles become smaller and weaker due to lack of use.
How common is spinal muscular atrophy?
Approximately 10,000 to 25,000 children and adults are living with SMA in the United States. It’s a rare disease that affects one out of 6,000 to 10,000 children.
Who might get spinal muscular atrophy?
A person with SMA inherits two copies of a missing or faulty (mutated) survival motor neuron 1 (SMN1) gene. One faulty gene comes from the mother and the other comes from the father. An adult can have a single copy of the defective gene that causes SMA and not know it.