SMA, also called Spinal Muscular Atrophy, is an uncommon disease that causes muscle wasting and weakness. The disease, which affects many muscles in the body and affects the ability to move, reduces the quality of life of people. SMA, which is considered the most common cause of death in infants, is more common in western countries. In our country, it is a genetically inherited disease that is seen in one baby in approximately 6 thousand to 10 thousand births. SMA is a progressive disease characterized by muscle wasting originating from motor neurons called movement cells. So what is SMA disease, what causes it? Is there treatment for SMA, what are the symptoms? Who gets SMA at what age? How many years do SMA patients live? Why is SMA treatment not available in Turkey?
What is SMA disease?
It is a genetically inherited disease that causes loss of spinal motor neurons, that is, motor nerve cells in the spinal cord, and causes weakness on both sides of the body, with the involvement of proximal muscles close to the center of the body, and progressive weakness and atrophy in the muscles, i.e. muscle loss. Weakness in the legs is more pronounced than in the arms. Since the SMN gene in SMA patients cannot produce any protein, the motor nerve cells in the body cannot be fed, and as a result, voluntary muscles become unable to function. SMA, which has 4 different types, is also known as "loose baby syndrome" among the people. In SMA, which makes eating and breathing impossible in some cases, vision and hearing are not affected by the disease and there is no loss of sensation. The person's intelligence level is normal or above normal. This disease, which is seen in every 6000 births in our country, is seen in the children of healthy but carrier parents. While parents are living their lives in a healthy way without realizing that they are carriers, SMA may occur when this defect in their genes is passed on to the child. The incidence of SMA in children of carrier parents is 25%.
What are the symptoms of SMA disease?
Symptoms of Spinal Muscular Atrophy can vary from person to person. The most common manifestation is muscle weakness and atrophy. There are 4 different types classified according to the age of onset of the disease and the movements it can make. While the weakness in type-1 patients seen in the neurological examination is general and disseminated, in type-2 and type-3 SMA patients, weakness is seen in the proximal muscles close to the trunk. Typically, tremors and tongue twitches may occur. Depending on the weakness, scoliosis, also called spinal curvature, can be seen in some patients. The same symptoms can be seen in different diseases. Therefore, the patient's history is listened to in detail by a specialist neurologist, his complaints are examined, EMG is performed, and laboratory tests and radiological imaging are applied to the patient when deemed necessary by the physician. With EMG, the neurologist measures the effect of electrical activity in the brain and spinal cord on the muscles in the arms and legs, while the blood test determines whether there is a genetic mutation. In general, although the symptoms vary according to the types of the disease, they are listed as follows:
- Weak muscles and weakness leading to lack of motor development
- decreased reflexes
- shaking hands
- Inability to maintain head control
- feeding difficulties
- Weak voice and weak cough
- Cramps and loss of walking ability
- lag behind peers
- frequent falls
- Difficulty sitting, standing and walking
- tongue twitch
What are the types of SMA disease?
There are four different types of SMA disease. This classification represents the age at which the disease begins and the movements it can make. The older the age at which SMA shows its symptoms, the milder the disease. Type-6 SMA with symptoms in infants aged 1 months and younger is the most severe. In type-1, slowing of baby movements can be observed in the last stages of pregnancy. The most common symptoms of type-1 SMA patients, also called hypotonic infants, are lack of movement, lack of head control, and frequent respiratory tract infections. As a result of these infections, the lung capacity of the babies narrows and after a while they have to take respiratory support. At the same time, arm and leg movements are not observed in babies who do not have basic skills such as swallowing and sucking. However, they can make eye contact with their lively gaze. Type-1 SMA is the most common cause of infant death worldwide.
Type-2 SMA It is seen in babies aged 6-18 months. While the baby's development is normal before this period, symptoms begin in this period. Although type-2 patients who can control their heads can sit alone, they cannot stand and walk without support. They do not verify on their own. Tremors in the hands, inability to gain weight, weakness and cough can be observed. Type-2 SMA patients, in which spinal cord curvatures called scoliosis can also be seen, often have respiratory tract infections.
Type-3 SMA The symptoms of patients begin after 18 months. Babies with normal development until this period may find the signs of SMA to be noticed in adolescence. However, his development is slower than his peers. As the disease progresses and muscle weakness develops, difficulties such as difficulty in standing up, inability to climb stairs, frequent falls, sudden cramps, and inability to run are encountered. Type-3 SMA patients may lose their walking ability in advanced ages and may need a wheelchair and scoliosis, that is, spinal curvature may be observed. Although the respiration of this type of patients is affected, it is not as intense as in type-1 and type-2.
Known for showing symptoms in adulthood, type-4 SMA is less common than other types and the progression of the disease is slow. Type-4 patients rarely lose the ability to walk, swallow and breathe. In the type of disease where weakness can be seen in the arms and legs, spinal cord curvature can be seen. In patients with tremor and twitching, usually the muscles close to the trunk are affected. However, this condition gradually spreads throughout the body.
How is SMA disease diagnosed?
Since spinal muscular atrophy disease affects movement and nerve cells, it is usually noticed when bilateral weakness and limitation of movement occur. SMA occurs when the mutated gene is passed from both parents to the baby when the parents decide to have a baby in their lives, which they continue without being aware of the fact that they are carriers. In case of genetic transmission from one of the parents, carriers can occur even if the disease does not occur. Nerve and muscle measurements are made with EMG after parents see an abnormality in their baby's movements and apply to the doctor. When abnormal findings are detected, suspicious genes are examined with a blood test and a diagnosis of SMA is made.
How is SMA disease treated?
There is no definitive treatment for SMA disease yet, but studies are continuing at full speed. However, the quality of life of the patient can be increased by applying different treatments to reduce the symptoms of the disease by the specialist physician. Raising awareness of the relatives of the patient diagnosed with SMA about care plays an important role in facilitating home care and increasing the quality of life of the patient. Since type-1 and type-2 SMA patients are usually lost due to lung infections, it is extremely important to clean the airways of the patient in case of irregular and inadequate breathing.
SMA disease medication
Nusinersen, which was approved by the FDA in December 2016, is applied in the treatment of infants and children. This drug aims to increase the production of the protein called SMN from the SMN2 gene and to provide cell nutrition, thus delaying motor neuron deaths and thus reducing symptoms. Nusinersen, which was approved by the Ministry of Health in July 2017 in our country, has been used in less than 200 patients worldwide in a few years. Although the drug has received FDA approval without distinguishing between SMA types, there are no studies on adult patients. Since the effects and side effects of the drug, which has a very high cost, are not fully known, it is considered appropriate to be used only for type-1 SMA patients until its effects on adult SMA patients are clarified. For a healthy and long life, do not forget to have your routine check-ups with your specialist physician.
SMA Gene Therapy
The USA was the first country to approve gene therapy. The USA approved in May 2019, Japan in March 2020, and the European Union in May 2020. While the USA and Japan apply gene therapy to SMA patients under the age of 2; Europe applies it to all SMA patients under 21 kilograms.
Is There SMA Treatment in Turkey?
Minister Koca also stated that the Scientific Committee recommended the use of a second drug that has shown its effect for SMA patients, and said, “We have started the procedures for the use of this drug.”
How many years do SMA patients live?
Babies with type 0 SMA mostly die within the first 6 months of life. In type 1 SMA patients, life expectancy is approximately 3 years with the help of nutritional support, respiratory support and supportive treatment.
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