Spinal muscular atrophy (SMA) is classified as a motor neuron disease as it involves the loss of nerve cells called motor neurons. It is a genetically acquired condition that affects the central nervous system, voluntary muscle movements, and peripheral nervous system. Therefore, SMA results in muscles getting smaller because they are not stimulated by nerve cells. The rare complication affects 1 in 6,000 to 10,000 children in the country.

Causes
A healthy SMN1 gene produces the SMN protein, which is required by motor neurons to survive and function appropriately. Healthcare experts indicate that the most viable cause of spinal muscular atrophy is a deficiency of the SMN protein. Children with SMA usually lack part of the SMN1 gene or have changed (mutated) genes. Therefore, people with spinal muscular atrophy do not create sufficient SMN protein, which could cause the motor neurons to shrink and cease to exist. As a result, the individual’s brain might be unable to control voluntary movements, especially motions associated with the neck, arms, legs, and head.

Types
There are four common types of SMA that one may develop.

• SMA Type 1
  This type of SMA is severe and may occur in infants within the first six months of their life. Some kids with SMA type 1 may also have a severely low mortality rate, but aggressive therapy might help improve their outlook and care for them.
• SMA type 2
  If a child develops spinal muscular atrophy between six and 18 months, the condition is classified as type 2. These affected children might be able to sit up but face trouble with respiration. This might also put their lives at risk as the disease progresses.
• SMA type 3
  Children 18 months of age or older may show signs of SMA type 3. This condition might become prominent as they reach their teenage years. Muscle weakness is a common indicator of the disease and most patients might be able to walk and stand for limited periods. This is commonly experienced in the early stages of spinal muscular atrophy type 3.
• SMA type 4
  This type is noticed in adults. Moreover, SMA type 4 is rarely severe enough to have an impact on the patient’s lifespan.

SMA is not associated with chromosome 5
SMA isn’t always caused by gene mutations or a deficiency of the SMN protein. So, people who develop other forms of spinal muscular atrophy, such as Kennedy’s disease, might experience a different severity. Others might experience symptoms in muscles farther away from the center of the body than those associated with SMA types 1 through 4.

Symptoms
The signs and symptoms of spinal muscular atrophy may vary from one person to the other. They might also be mild or disabling but involve a weakness of the muscles responsible for muscle control. One may not experience involuntary movements in regions like the blood vessels, digestive tract, and heart. However, the disease may weaken muscles closer to the center of the body, including the hips, thighs, shoulders, and upper back. Furthermore, children affected by SMA may develop a curve in the spin following the loss of size and strength of the back muscles. It may also affect breathing and swallowing, putting one’s life at risk.