Spinal Muscular Atrophy (SMA) is an inherited neurodegenerative disorder that affects voluntary muscle movement, resulting in progressive muscle weakness and atrophy; and robs people of physical strength by affecting the motor nerve cells in the spinal cord, taking away the ability to walk, eat, or breathe.
SMA is the leading genetic cause of death in infancy, and it is estimated that 1 in 50 Americans is a gene carrier. While in the past, infants with SMA typically did not survive more than two years, today most doctors now consider SMN-related SMA to be a continuum and prefer not to make rigid predictions about life expectancy or weakness based strictly on age of onset.
What causes SMA?
Chromosome 5 SMA is caused by a deficiency of a motor neuron protein called SMN, for “survival of motor neuron.” This protein, as its name implies, seems to be necessary for normal motor neuron function. Its deficiency is caused by genetic flaws (mutations) on chromosome 5 in a gene called SMN1. The most common mutation in the SMN1 gene within patients diagnosed with SMA is a deletion of a whole segment, called exon 7.1 Neighboring SMN2 genes can in part compensate for nonfunctional SMN1 genes as there is 99% identity between these two genes.
The primary symptom of chromosome 5 SMA is weakness of the voluntary muscles. The muscles most affected are those closest to the center of the body, such as those of the shoulders, hips, thighs, and upper back. The lower limbs seem to be affected more than the upper limbs, and deep tendon reflexes are decreased.
Meanwhile, sensory, mental, and emotional functioning are entirely normal for people suffering from the chromosome-5 SMA.
What are the symptoms of SMA?
- Muscle weakness and atrophiation
- Special complications occur if the muscles used for breathing and swallowing are affected, resulting in abnormalities in these functions. If the muscles of the back weaken, spinal curvatures can develop.
Treatment of SMA:
By this year, the FDA has approved three medications to treat SMA: nusinersen (Spinraza), onasemnogene abeparvovec-xioi (Zolgensma) and risdiplam (Evrysdi). Both are forms of gene therapy that affect the genes involved in SMA.
If you or a loved one has been diagnosed with SMA, it is essential to seek medical care and explore available treatment options. Early intervention and comprehensive management can help minimize symptoms, slow the progression of the disease, and provide a better quality of life.
Collaboration with healthcare professionals who specialize in SMA can provide valuable guidance and support throughout the journey.
Remember, every step towards managing SMA is a step towards a brighter future. Together, we can continue to raise awareness, support ongoing research, and provide individuals with SMA the best possible care and treatment options.