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Spinal Muscular Atrophy (SMA)

Spinal Muscular Atrophy (SMA)

What is SMA? 

Spinal Muscular Atrophy (SMA)  is a genetic condition which is a hereditary motor neuron disease that affects the individual's central nervous system, peripheral nervous system and voluntary muscle movement (skeletal muscle).

Is SMA a Genetic Disease?

The most common form of SMA originates from the SMN1 and SMN2 genes in 13 regions on the long arm of the 5th chromosome. It occurs as a result of homozygous deletions or minor mutations of the SMN1 and SMN2 genes. The disease is transmitted by autosomal recessive genes of the parents.  If both parents are carriers, they have a 25% chance of having a child with SMA, 25% chance of having a healthy child and 50% chance of a carrier child like the parents. 

What is the incidence of SMA ? 

SMA is one of the rare diseases among 7000 rare diseases where the term rare disease varies from country to country.

SMA disease, which is seen in one in 6,000 to 10,000 babies in our country, is one of the most known also rare diseases. Because the number of known registered patients in the health system  is around 3000.

What are the different types of SMA?

The symptoms of this disease are divided into five different types, from 0 to 4, according to the age of onset, the rate of spread and the mobility of the individual.

Type 0: Characterized by decreased fetal motility in late pregnancy, in which case preterm birth is common. These newborns may have severe weakness, hypotonia, and heart defects, while difficulty in breast feeding, breathing and swallowing. Babies diagnosed with type 0 SMA disease usually die within the first six months.

Type 1: The appearance of symptoms of SMA disease at significant levels between six months and one year after birth, indicates type 1 SMA disease. These children are often very frail, have difficulty in breast feeding, breathing and swallowing beside never reach the sitting stage of developmental progress on their own.

Type 2: Symptoms begin between 6 months and 18 months in patients. Unfortunately, 70% of patients only live up to the age of twenty-five.

Type 3: Symptoms usually appear between 18 months and adulthood. During these periods, affected individuals gained the ability to act independently. Life expectancy may be normal.

Type 4: Occurs at the end of adolescence or adulthood. Patients can reach any stage of movement development and commonly maintain their ability to move for life. Life expectancy is normal.

What are the symptoms of SMA?

Symptoms of SMA disease cover a wide spectrum, depending on the type and severity of the disease. The most prominent symptom of SMA disease is muscle weakness. The muscles most affected by this disease are those closest to the center of the body, such as the shoulders, hips, thighs, and upper back.

In particular, the most important complication of the disease is the loss of function of the muscles that control respiration. Symptoms of respiratory muscle weakness include headaches, difficulty sleeping and insomnia at night, frequent yawning during the day, excessive sleepiness during the day, poor concentration, difficulty lying flat, chest infections, and eventually heart damage and respiratory failure.

Scoliosis, or curvature of the spine, is also a common problem in SMA and requires medical attention.

The senses of sight, hearing, taste, smell, and touch, as well as mental and emotional functioning, are completely normal in individuals with SMA.

What are the Diagnostic Methods of SMA disease?

The first step in diagnosing any neuromuscular disease is usually a physical examination and obtaining the patient's family medical history. Muscle weakness and hypotonia in infants are often the first signs of SMA disease. Movement difficulties include loss of motor skills, proximal muscle weakness, and absence of reflexes.

In the laboratory, an enzyme called creatinine kinase (CK), is elevated in the muscles, but it is not specific to this disease.

Other tests include nerve signal conduction velocity testing and tests that measure electrical activity in the muscle called electromyography or EMG.

Definitive diagnosis is made by genetic testing methods. 

Sanger Sequencing,  MLPA method and Next Generation Sequencing methods are used as gold standards in genetic diagnosis to detect deletions and mutations in SMN genes.

Supportive treatments and rehabilitation methods are used in treatment.

In our center, SMA carrier screening tests are performed in premarital and pre-pregnancy spouses as well as individuals with suspected disease.

What are the Treatment Methods for SMA?

  • SMN Modification: Antisense Oligonucleotides
  • SMN Gene therapy methods
  • Stem Cell transplant
  • Protection of Nerve Cells
  • Protection of the Neuromuscular Junction
  • Muscle-strengthening treatments


How can SMA Disease be prevented?

SMA is a difficult and expensive disease to treat. Maintaining quality of life is difficult for both patients and families. As with many diseases, preventive methods are always cheaper and more practical than treatment methods.

The annual treatment cost of an SMA type 1 patient ranges from 75,047 to 196.429 USD, with an average of 125,000 USD.

The cost of the SMA carrier screening test to be performed on couples is 125 USD, that is, with the money needed for the treatment of a patient, 1000 people can be tested for SMA screening and the probability of having a sick child is reduced.

Other methods to prevent SMA disease are;

Community Education

Health Personnel Training

Detailed explanation of Hereditary Diseases

Reducing Consanguineous Marriages

Community Screenings

Premarital screenings

Family Screenings

Newborn Screenings

Genetic Counseling

Prenatal Diagnosis

Pre-Implantation Genetic Diagnosis

Because SMA is an inherited diseases, genetic counseling should be given to all families and married couples before having a child. Career Screening tests should be considered and done to couples. 

Diagnosis of the baby should be made in the 3-4th months of pregnancy with prenatal diagnosis method, if the child is sick, child birth should be prevented by medical intervention or the family can have a healthy child with the IVF method performed by extracting the genes.

In the commission established in the Grand National Assembly of Turkey between 2019 and 2020, it was decided that community education for rare diseases, genetic counseling and genetic tests before marriage or pregnancy should be done so that the birth of sick children can be prevented.

Although it is one year late in this regard, the Ministry of Health has included SMA carriage among premarital tests in the past few weeks, and has also included it in the screenings of newborns.

We perform these tests on individuals who apply to our center before marriage or before pregnancy.

In our center, SMA carrier screening tests are performed in premarital and pre-pregnancy spouses as well as individuals with suspected disease.

For more information, for genetic testing and genetic counseling  please contact with us. 

Last Update: 2023-04-18 15:53:51