Spinal muscular atrophy (SMA) is recognized as a rare condition characterized by motor neuron and nerve cell loss in the spinal cord. It is a genetic neuromuscular disease that leads to wasting away and weakening muscles. It has been found that nearly 10,000 to 25,000 children and grown-ups in the country live with this condition. Read further to learn about the disorder, its causes, and associated risk factors.

Structural causes
Lack of muscle movement is the primary cause of atrophy in SMA. Typically, healthy muscles receive signals from the motor neurons in the spinal cord and move in response to these signals. In SMA, the degeneration of motor neurons occurs, and the major cause of this is the lack of a protein called SMN (Survival Motor Neuron). Without this protein, the motor neurons would lose their function and structure. It prevents the motor signals from the brain from reaching the nerves. It causes a lack of movement of the skeletal muscles, which leads to the shrinking and weakening of the muscles, called atrophy. Hence, lack of muscle movement is the primary reason for atrophy.

Genetic causes
There are genetic causes of spinal muscular atrophy. Children inherit SMA from their parents, which is present at birth. The changes or mutation in the SMN1 gene is responsible for the SMA. This gene helps in brain cell survival, which helps in communication with the muscles. It has been found that a homozygous mutation of the SMN1 gene triggers spinal muscular atrophy in more than 94% of the cases. The homozygous mutation signifies that the child has inherited the identical or similar version of this mutated gene from their parents. The SMN1 and SMN2 genes play an essential role in the production of the SMN protein. The SMN1 gene is primarily responsible for SMN protein production, while the SMN2 gene plays a minor role in its production. Though the protein produced by the SMN2 gene is less stable and shorter, it helps deal with the SMN protein deficiency in case the SMN1 gene is altered.

How is SMA inherited?
The causes of spinal muscular atrophy may get more evident once you know how it is inherited. Every person receives two copies of the SMN1 gene, one from each parent and one to two copies of the SMN2 gene. Sometimes, it has been found that some people may have up to eight copies of the latter. When an altered SMN1 gene is inherited from both parents, it leads to an SMN protein shortage. If there are one or two copies of the SMN2 genes, there are chances of more SMN protein deficiency, leading to severe spinal muscular atrophy. Mild SMA occurs when there is the presence of three or more copies of the SMN2 gene that makes up for the lack of the SMN protein. Therefore, the mutation in the SMN1 gene will determine whether a person has SMA, and the number of SMN2 genes will determine the severity of the condition.

Risk factors
It has been found that some lifestyle habits are linked to certain motor neuron diseases. However, researchers are yet to determine whether these factors are connected to or are triggers of spinal muscular atrophy. But certain lifestyle habits, like unhealthy meals, lack of physical activity, or exposure to contagious infections, may be linked to the complications and other health issues caused by this condition.

Unhealthy meals
Spinal muscular atrophy may worsen when meals do not provide sufficient nutrition or meal plans are not balanced. It is because the body will not be able to fight infections or have enough energy, thus increasing the chances of SMA complications. Therefore, eating healthy and balanced meals is essential to keep the condition at bay.

Exposure to contagious infections
People diagnosed with spinal muscular atrophy should avoid those with contagious or infectious diseases because a few health conditions can worsen SMA or increase complications.

Lack of activity
It has been found that SMA does not affect the intellect or the sensory nerves, and many people with it are highly intelligent. However, an unhealthy lifestyle and lack of physical activity increase the complications caused by spinal muscular atrophy. Muscle function can be improved and promoted by opting for exercises and activities suited to one’s capabilities.

Though some of the common causes of spinal muscular atrophy and lifestyle risk factors that may worsen the condition are described above, sometimes, rare genetic causes such as the two genes – UBE1 and DYNC1H1 may also be responsible for this condition. Therefore, it is suggested to consult a healthcare expert and get the proper treatment based on the cause, severity, and type.