By Gary Levine
Spinal Muscular Atrophy (SMA) is a genetically-transmitted, lower-motor-neuron disease that causes progressive degeneration of muscles through deterioration and loss of specialized nerve cells. The majority of muscle-controlling nerve cells, also called “motor neurons,” are located in the spine. This form of Muscular Dystrophy prevents muscles from receiving signals from these nerve cells causing weakness and an inability to perform motor skills.
August is Spinal Muscular Atrophy Month and, with the coming of the annual Labor Day MDA Telethon, it is imperative to bring attention to this abhorrent disease.
SMA is a recessive genetic disease…so both parents must carry of copy of the SMA gene. Healthy and normal movement requires a protein called SMN (Survival Motor Neuron). The protein is controlled by the SMN 1 gene and we require two copies of this particular gene…one from each parent…for the orderly production of the protein. When only one parent has faulty copy of this gene…the “SMA” gene…they are considered a carrier of SMA. Their child will, as a result, have one faulty SMN 1 gene…making them a carrier, as well.
When both parents carry the faulty SMN 1 gene, their offspring will likely have Spinal Muscular Atrophy. Should the child receive two faulty SMN 1 genes, they will produce reduced amounts of the aforementioned SMN protein…causing a deterioration of lower-motor-neurons within their spinal cord…which will ultimately result in an inability to generate muscle movement and atrophy of those muscles.
The most common form of SMA is “chromosome 5 SMA.” As a result of varying symptoms, rates of progression and ages of commencement, SMA is categorized in four types:
