There is a kind of weakness called SMA. Do you know about this rare disease?

The last day of February every year is International Rare Disease Day. Rare diseases, also known as "orphan diseases," refer to diseases with very low prevalence rates.

For most rare diseases, ordinary people may never have even heard of them, let alone encountered them, such as SMA.

“Type 1 envies Type 2 for being able to sit, Type 2 envies Type 3 for being able to stand, Type 3 envies Type 4 for being able to walk, and Type 4 envies normal people.” This is the sad insight of a mother of a child with SMA.

What exactly is SMA?

SMA generally refers to spinal muscular atrophy, which is an autosomal recessive hereditary neuromuscular disease. Due to damage to the motor nerves, muscles will become weak and atrophied, which will affect the patient's ability to walk, eat and even breathe. Mild cases may manifest as limb weakness, and severe cases often die from respiratory failure. Approximately one in every 10,000 live births will be diagnosed with SMA, and it is also one of the most common genetic diseases that lead to infant death.

The pathogenesis of SMA is that the SMN1 gene located in the chromosome 5q13 region is missing or mutated, which damages the motor neurons and affects the contraction function of the muscles. According to the patient's age of onset and clinical course, SMA can be divided into four types from severe to mild:

Type 1, or infantile type, accounts for about 45% and is the most serious. It occurs within 6 months of birth and progresses rapidly, making it impossible for infants to sit alone. Without treatment, most infants will not live past the age of 2, and most die of respiratory failure.

Type 2, the intermediate type, accounts for about 30%-40%. It usually starts 6-18 months after birth. The maximum motor ability of the child is to sit alone. Some children lose the ability to sit alone in childhood. Although their life span is shortened, most can live to adulthood.

Type 3, or adolescent type, accounts for about 20%. It usually starts 18 months after birth, with normal early motor development and the patient can walk independently. As the disease progresses, the patient gradually loses the ability to walk and becomes dependent on a wheelchair, with life expectancy remaining the same or slightly reduced.

Type 4, the adult form, has normal early motor development, onset in adulthood, proximal limb weakness, slow progression, and no shortening of life expectancy.

How to treat and prevent SMA?

In the past, SMA was difficult to diagnose, and even if it was diagnosed, there was no cure. Hospitals could only provide "multidisciplinary management" for SMA patients, such as respiratory management, nutritional management, bone management and other symptomatic auxiliary methods.

But after the advent of nusinersen injection, this disease has a cure. Nusinersen injection is used to treat 5qSMA. It was approved in the United States on December 23, 2016 and launched in China on April 28, 2019. The drug is available, but it is very expensive. The price of about 700,000 yuan per injection and the treatment method of "6 injections in the first year, 3 injections per year thereafter, and lifelong medication" make many people discouraged.

If you can't afford the high cost of medicine, you can only give your child rehabilitation training. Many SMA children have life-saving equipment such as ventilators, expectorants, suction machines, nebulizers, and auxiliary equipment such as standing frames, sitting correction chairs, and ankle-foot orthoses at home. All of this is just to buy more time for the child. The sudden end of life is the real fate of most severe SMA patients.

On December 3, 2021, the National Health Insurance Administration announced that nusinersen injection was officially included in the medical insurance. The once sky-high price of 700,000 yuan per injection has been reduced to 33,000 yuan after the medical insurance experts bargained hard, giving SMA patients more hope of survival.

In addition, it is crucial to do a good job in SMA prevention. For families where both spouses are confirmed to be dual carriers of the SMA pathogenic gene through screening, SMA prenatal diagnosis and diagnosis reports are provided to those who are pregnant or preparing to be pregnant to prevent birth defects and form a closed loop of SMA screening. For example, as early as 2008, the American College of Medical Genetics began to promote universal screening for SMA carriers and achieved significant results.

At present, SMA screening has been launched in some provinces and cities in China. If you want to be screened for SMA carriers before marriage or pregnancy, you can go to nearby tertiary hospitals and maternal and child health hospitals for consultation.

Strengthening prenatal screening and newborn genetic disease screening can achieve eugenics and early detection and treatment of rare diseases. I hope more families can avoid tragedy from happening again.