What is SMA?
Spinal Muscular Atrophy (SMA) is a common human genetic disease that affects the anterior horn cells of the spinal cord. It is characterized by the progressive degeneration of the motor neurons with consequent paralysis of the trunk and limbs. SMA affects the body’s voluntary muscles. However, mental ability, sight, and facial muscles, with the exception of the tongue, are not affected. The disease is not well known since 50% of diagnosed babies die before the age of 2. Approximately one in 6,000 children is affected, and approximately one in 40 person carries the gene that causes SMA.
SMA type I, also known as Werdnig-Hoffmann Disease, is the most severe form of SMA and defined as children who are not able to sit independently. Children with SMA type I usually present to the doctors before six months of age because of their severe low muscle tone, breathing difficulties, lack of reflexes, and spontaneous tongue movements (referred to as tongue fasciculations). Due to respiratory problems, children with SMA type I often have a significantly shortened life span.
SMA type II is an intermediate form of SMA and is defined as children who can sit unassisted but cannot walk or stand. Children with this form of SMA usually present to the doctors between 6 and 18 months of age because of low muscle tone and delayed gross motor skills. Individuals with SMA type II often have tongue movements and minor hand tremors. SMA type II can also cause varying degrees of breathing difficulties. Many cases of SMA type II children experience a shortened lifespan.
SMA type III, also known as Kugelberg-Welander Disease, is the least severe form of SMA and is defined as individuals who are able to stand and walk unassisted. Usually individuals with this form of SMA have limited, if any, breathing difficulties, and may show little or no decline. This form of SMA often resembles muscular dystrophy but can be identified by specialized testing.
Presently, there is no cure for SMA.
Treatment of SMA is symptomatic and supportive and may include treating pneumonia, scoliosis, and respiratory infections, if present. Physical therapy, orthotic supports, and rehabilitation is needed. Current research efforts investigate a variety of potential drug treatments. In addition, Aurora Biosciences/FMSA is using a high throughput drug screen to identify promising drug compounds that may help treat SMA.
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