WHAT IS SMA?

SMA, or Spinal Muscular Atrophy, is a neuromuscular disease, specifically classified as a motor neuron disease.  Those with the disease are missing the SMN1 gene or have a damaged SMN1 gene, and are genetically unable to produce enough SMN (Spinal Motor Neuron) protein, which is a protein that keeps spinal motor neurons alive and functioning.  Spinal motor neurons are the cells that send signals to the muscle fibers in the body.  Without enough SMN protein, the neurons gradually die off, and the person loses the ability to use the muscles they were attached to.  The muscles weaken and "atrophy."

Humans have "backup" SMN2 genes that also produce SMN protein if the SMN1 gene is missing or damaged (if the person has SMA.)  The number of SMN2 genes a person has and the amount of protein they can produce dictates the severity of the disease.  SMA has been classified into types:  Type 1 is the most severe, and Type 4 is the least.  Those with many copies of the SMN2 gene can live well into adulthood before symptoms even start, and they are classified as Type 4.  Statistics say that those diagnosed with Type 1 before the age of two have only a 50% chance of making it to the age of two, as most of their muscles, including their lungs, will be severely weakened.

There is much more to learn about SMA, and the national FSMA website has this information:  http://www.fsma.org