SMA is a genetic disease that attacks nerve cells, called motor neurons, in the spinal cord. These neurons communicate with the muscles, especially in the arms and legs. SMA weakens muscles and can affect walking, crawling, breathing, swallowing, and head and neck control. There are many types of SMA, and some of them are fatal. Life expectancy depends on the type of SMA and how it affects breathing. There is no cure, although some treatments can be helpful.
SMA is caused by a mutation in the gene SMN1. This mutation decreases the amount of a specific protein in the nerve cells. In a mouse model of SMA, scientists supported through the NICHD’s Intellectual and Developmental Disabilities Branch were able to use a drug to stimulate production of the protein, and as a result the treated mice lived longer than those who did not receive the treatment. To understand how timing of treatments affects survival, researchers treated mice with SMA at different time points after birth. It was found that early treatment, given for a short time, resulted in the longest survival for the affected mice.
The development of similar treatments in humans could help improve survival rates in infants born with SMA (PMID: 21672919).