How much do you know about spinal muscular atrophy (SMA)?

In 2021, a special medicine called "Nosinersen Sodium Injection" that can treat the rare disease "Spinal Muscular Atrophy" became completely popular.

Not only because it brings hope to the families of SMA patients, but also because this high-priced special medicine has finally been included in the national medical insurance catalog. The discounted price has attracted countless heated discussions, and SMA has also attracted public attention. So what is SMA? Today, let us walk into the world of SMA!

What is SMA?

Spinal muscular atrophy (SMA) is a severe, lethal and disabling single-gene autosomal recessive genetic disease that causes muscle weakness and atrophy in patients due to the degeneration of motor neurons. It is the leading genetic cause of death in infants under 2 years old and there is currently no cure.

What are the characteristics of SMA?

The incidence of SMA in newborns is about 1/6000-1/10000. One in every 40-50 people in the general population carries the SMA gene . If both spouses carry the SMA gene, there is a 1/4 chance of giving birth to a sick baby, a 1/2 chance of giving birth to a carrier baby, and a 1/4 chance of giving birth to a healthy baby. SMA patients may not have any symptoms or manifestations during the fetal and neonatal periods, and cannot be detected through routine prenatal examinations (such as B-ultrasound), and are extremely hidden.

Clinical manifestations and classification?

The onset age of SMA patients varies greatly, ranging from before birth to adulthood. It can be divided into five types:

There is a protein called "survival motor neuron (SMN)" in the human body. The normal amount and function of this protein are the prerequisites for the free movement of human muscles. Once it is deficient, it will cause the death of motor neurons in the anterior horn of the spinal cord, causing muscle atrophy and leading to the occurrence of SMA.

About 90% of SMN protein is produced by the survival motor neuron gene 1 (SMN1), and a small part is produced by gene 2 (SMN2). Therefore, when the SMN1 gene is missing, only a small amount of complete SMN protein can be transcribed by the SMN2 gene, but these proteins are not enough to maintain normal human activities. Therefore, the number of SMN2 genes will directly affect the onset of SMA and the severity of the disease.

How can SMA be prevented?

Given the severity of SMA and its preventable and controllable characteristics, it is a consistent practice both at home and abroad to screen SMA carriers for the childbearing population, assess the genetic risk of having an SMA child, perform prenatal diagnosis when necessary, and prevent the birth of an SMA child.

How is SMA treated?

Regardless of the type of SMA, there is currently no effective treatment, which mainly focuses on symptomatic treatment, supportive treatment, rehabilitation treatment, etc., and actively prevents and treats complications.

"No small group should be abandoned." We call on society to pay more attention to this special group, advocate carrier screening and prenatal diagnosis for high-risk groups, scientifically prevent the occurrence of SMA, and make rare diseases no longer scary.