West Virginia Office
of Laboratory Services
167 11th Ave
South Charleston, WV 25303
Spinal muscular atrophy (SMA) is a group of inherited conditions that affect the motor neurons of the spinal cord. Motor neurons are specialized nerve cells that control the muscles used for activities such as breathing, crawling, and walking. In people affected by SMA, the loss of motor neurons leads to progressive muscle weakness and atrophy (wasting).
There are four primary forms of SMA which are classified based on the severity of the condition and the age at which symptoms begin. The symptoms and long-term outlook of each form vary widely. In general, forms of SMA with an earlier age of onset are more severe and have a greater impact on motor function. Early detection and treatment of SMA is important since studies suggest that therapy is most effective when started in the first few months of life.