SMA , which usually begins to show symptoms in infancy  , is one of the most common causes of infant mortality. SMA, a disease that affects the mobility of many muscles in the body, significantly impacts a person's quality of life. SMA is a genetically transmitted disease that occurs in approximately one in 6,000 to 10,000 births in Turkey, but is more common in Western countries. 

What is SMA Disease?

Spinal Muscular Atrophy (SMA) is a rare disease that causes muscle loss and weakness.  SMA is a genetic disorder that causes the loss of motor nerve cells in the anterior horn of the spinal cord, leading to progressive weakness and atrophy in the central nervous system, peripheral nervous system, and skeletal musculature. While there is no definitive cure for SMA, there are treatments that can help manage symptoms.

The genetic factor responsible for the development of SMA is a genetic defect in the SMN1 gene, located on chromosome 5. The SMN1 gene is responsible for producing a protein called SMN in the body. If this protein is not produced in sufficient quantities, motor neurons begin to deteriorate and die. When motor neurons in the spinal cord begin to shrink and die, the brain becomes unable to control the body's voluntary muscles. This causes the muscles to weaken over time. 

Protein: Its Functions and Importance

SMA doesn't affect vision or hearing, doesn't cause sensory loss, and doesn't affect intelligence. However, it often causes difficulties with eating and breathing.

What are the symptoms?

The symptoms of SMA can vary from person to person. However, the most common symptoms are muscle weakness and atrophy. The later the symptoms of SMA are detected, the milder the disease. Generally, the symptoms of SMA can be listed as follows:

• Weak muscles leading to lack of motor development,
• Decreased reflexes,
• Tremors in the hands,
• Difficulty in head control,
• Difficulty in feeding,
• The weak voice,
• Weak cough,
• Cramps,
• Loss of walking ability,
• Don't fall behind your peers,
• Frequent falls, difficulty in sitting, standing and walking,
• Twitching of the tongue.

What are the Types of SMA Disease?

SMA disease is divided into four different types, depending on the age at which the disease begins and movement restrictions.

Type-1 SMA

This is the most severe type of SMA, with symptoms appearing in babies 6 months of age and younger. A slowdown in fetal movement may also be observed in the later stages of pregnancy. The most significant symptoms of type 1 SMA, also known as a floppy baby or hypotonic baby, include decreased mobility, inability to maintain head control, and frequent respiratory infections. 

Frequent infections can lead to a decrease in babies' lung capacity, and eventually, they may require respiratory support. Other observed symptoms include an inability to perform basic skills such as swallowing and sucking, and an inability to move their arms and legs. However, they can maintain eye contact with others. Type 1 SMA is one of the most common causes of infant mortality worldwide.

Type-2 SMA 

Symptoms appear between 6 and 18 months of age.  Before the onset of SMA  symptoms, the baby's development is normal. During this period, they can control their head and sit independently. However, they cannot sit up without support, stand, or walk. Type 2 SMA presents with symptoms such as hand tremors, weight loss, weakness, and cough. Scoliosis, a spinal curvature, can also occur.

Type-3 SMA 

Symptoms usually begin after 18 months. However, sometimes symptoms can appear until adolescence. People diagnosed with type 3 SMA develop more slowly than their peers. As the disease progresses, they experience difficulties standing up, difficulty climbing stairs, falls, sudden cramps, an inability to run, and scoliosis. People with type 3 SMA may lose their ability to walk as they age and may require a wheelchair. While breathing is affected in this type of SMA, it is not as severe as in types 1 and 2.

Type-4 SMA

Symptoms appear in adulthood. It is less common than other types of SMA, and the disease progresses slowly. Patients with type 4 rarely experience problems with walking, swallowing, or breathing. Weakness in the arms and legs, tremors, twitching, and spinal curvature are most common. In type 4 SMA, the muscles near the trunk are generally affected, but the condition progresses slowly.

How is SMA Diagnosed?

The first step in diagnosing SMA  is usually a physical examination and a family medical history. After observing symptoms and completing the physical examination, some simple tests are performed to diagnose SMA.

To confirm a diagnosis of SMA,  your doctor   will first order a blood test to measure the levels of the enzyme creatine kinase (CK) in your muscles. However, a definitive diagnosis cannot be made based solely on the blood test results, as CK levels are elevated in many neuromuscular diseases.

Based on this data, doctors who suspect SMA may order genetic testing. Genetic testing is the most definitive way to diagnose SMA. Genetic testing is performed using a blood sample. In rare cases, doctors may order a muscle biopsy from the thigh.

Another method used to diagnose SMA   is an EMG test, which measures electrical activity in the muscle. This test is performed using short needles. 

What are the treatment methods?

Currently, there is no definitive cure for SMA. However, medical experts are continuing their efforts to find a definitive treatment.  The primary goal of SMA  treatment is to manage the symptoms and manage complications.

• Respiratory weakness is a significant problem in SMA. An oxygen mask or mouthpiece is used to control respiratory weakness. 
• People with SMA frequently experience respiratory infections. Therefore, while they should receive a flu vaccine every year, they should also take precautions such as avoiding crowds, getting enough rest, and eating a healthy diet.
• Babies with poor sucking and swallowing problems can often be fed through a feeding tube called a gastrostomy tube or G-tube. Consulting a speech-language pathologist can help prevent both swallowing and speech-related problems. 
• Some medical professionals believe that severe spinal curvatures can compress the lungs, leading to respiratory problems. To prevent this, a back brace or corset can be used to support the spine.
• The most important treatment for SMA  is Spinraza,  a drug designed to increase the SMN2 protein. Spinraza is recommended for use in SMA patients, especially those between the ages of 2 and 12. 
• It is important for treatment not to neglect routine check-ups.

SMA Disease Medicine

Nusinersen , approved by the FDA in December 2016, is the drug used for SMA. This drug is used to increase the production of the protein SMN and delay motor neuron death by providing cell nutrition. In our country, it was approved by the Ministry of Health in July 2017. While the drug does not differentiate between types of SMA, no studies have been conducted on its effects on adult patients. Therefore, it is recommended that it be used only in patients with type 1 SMA.