Spinal muscular atrophy (SMA) is a disease that affects the neurons in your spinal cord. Over time the disease can interfere with muscle control in any part of the body including those connected with breathing and swallowing. There are several types of SMA. The severity and progression of the disease depends on the type and how early symptoms first develop.
Spinal muscular atrophy is a genetic disease that runs in families. Often parents are carriers of the disease but show no symptoms. Genetic counseling can identify this disease in adult carriers and counseling can help you understand the risks of passing this disease to your children. Unfortunately, the first time this disease is discovered in a family is only after a child is diagnosed with the disease.
What Causes SMA?
Spinal muscular atrophy is one of several autosomal recessive genetic diseases. It is passed along to a child when both parents are carriers of a missing or mutated gene that affects the motor neurons in the spine. The mutated or missing gene is responsible for producing a protein responsible for the health production and function of the nerve fibers that begin in the spinal cord and branch out to all the muscles in the body.
With the gene mutation associated with SMA the lack of this protein results in nerve cells weakening and atrophying. This results in muscle weakness that generally progresses over time.
Autosomal recessive disorders are only passed along to children if both parents have the genetic defect. When both parents are carriers of the disease, a child has a one in four chance of inheriting the disease and showing some degree of symptoms.
Because genes come in pairs, an individual can have one set of healthy genes and one set of mutated genes without showing symptoms. An individual with one set of defective genes is known as a carrier. This means even though they show no signs of the disease, if they have children with another carrier, they can then pass the disease along to their children.
Testing for Spinal Muscular Atrophy
Diagnosing SMA is usually not done until symptoms are present and other conditions are ruled out. Because SMA is a genetic, a blood test is done that examines the SMN1 and SMN2 genes. Most individuals with spinal muscular atrophy are lacking the SMN1 gene or have a mutated SMN1 sequence.
An EMG test which measures the electrical activity in a muscle may be used to rule out other conditions that mimic SMA.
Prognosis for Individuals with SMA
Researchers have found that even though the SMN1 gene is the gene primarily responsible for producing the SMN protein for healthy muscle growth and development. There is also a smaller level of the SMN protein produced by the SMN2 genes.
Everyone has a certain number of SMN2 genes that continue to produce some protein. The number of SMN2 copies an individual has as well as the type of spinal muscular atrophy an individual is diagnosed with will determine their overall prognosis.
The key to maintaining as much muscular strength as possible is early diagnosis. Ongoing medical monitoring can go a long way in lessening the risk of life-threatening complications. A multi-directional team approach can help support parents in caring for their children and providing a quality of life that takes into consideration their individual challenges.
There is no cure for SMA or vaccine that can be given to prevent the disease.
For families already known to be carriers of SMA, genetic counseling can give a realistic idea of the chances for passing along the disease and help in determining the choices to be made.
Daniel Silvera is a young man who understands firsthand the challenges presented by this disease. Born with SMA and a quadriplegic for most of his 33 years of life, he has a unique perspective on the quality of life. His story challenges all of us to stop and re-examine the true meaning of life. You can read his story here.
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