SMA : Spinal Muscular Atrophy

This month is SMA, Spinal Muscular Atrophy Disease awareness month. To increase awareness Prof. Dr. Duran Canatan (Pediatric Hematologists & Geneticists) gave enlightening information about SMA disease on TRT Antalya radio today. This month, we wanted to inform you by using the data of the PREMARRIED SPINAL MUSCULAR ATROPHY CARRIER SCREENING PROGRAM FIELD GUIDE from the General Directorate of Public Health of the Ministry of Health.

What is SMA?

Spinal muscular atrophy (SMA) is a group of genetic diseases characterized by irreversible loss of cranial nerve motor nuclei and anterior horn motor neuron cells located in the spinal cord, resulting in muscle atrophy and muscle weakness.

What is the underlying genetic factor of the SMA disease?

 The most common form of the disease is caused by homozygous deletion or pathogenic variations in the 'Survival of Motor Neuron 1' (SMN1) gene, which is autosomal recessively inherited and located on chromosome 5q13.

What is the incidence of the SMA disease in the world and in our country?

SMA is a rare disease. In a large, multinational study with a large number of data for SMA carriage, the incidence was found to be 1/11,000. Although the incidence and carriage rates of SMA disease are not known clearly in our country, the annual number of new cases is around 150 new borns and approximately 3000 SMA patients are followed in our country.

What are the symptoms of the disease?

The most prominent clinical features of spinal muscular atrophy (SMA) disease are hypotonia, muscle weakness and muscle atrophy. Weakness is usually in the extremity, axial, intercostal and bulbar muscles, and is in the form of a symmetrical weakness in the proximal muscles.

While hypotonia, weakness, respiratory and feeding problems are prominent in early-infancy, retardation in gross-motor developmental stages, frequent falls, delay in independent walking may be among the presenting symptoms in late-infancy and childhood.

Progressive muscle weakness, muscle atrophy and denervation findings, spinal deformities, scoliosis, and contractures may attract attention in the adolescent and advanced age group.

Classically, the disease is classified according to the age of onset and the maximum motor developmental stage gained. From the form with onset in the intrauterine period (SMA type 0), to forms with onset in the neonatal and early-infancy (SMA type 1), childhood (SMA type 2 and 3), adolescent and adult (SMA type 3) and adult (SMA type 4) periods that the disease may present in a broad spectrum.

How is the SMA disease diagnosed?

The diagnosis of SMA is based on the history, symptoms, and clinical findings as well as clinical examination findings of the patient. Definitive diagnosis is made by MLPA diagnostic method. In 95% of the cases there is a homozygous deletion of the SMN1 gene located in the chromosome 5q13 region. 

Is it possible to prevent the SMA disease? YES

It is possible to prevent the SMA disease with community education, pre-marriage or pre-pregnancy screening programs and genetic counseling should be given if both couples are carriers where the child will be 25% sick. Prenatal Diagnosis (PNT) method or In vitro fertilization method (Preimplantation Genetic Diagnosis: PGD) performed by gene extraction is recommended for couples to have a healthy child. 

Is there a definitive treatment for the SMA disease?

Life support programs and physical therapy programs are applied to SMA patients, but the definitive treatment is gene therapy fort he SMA patients.

In conclusion and our final message to the all young couples is to stay away from consanguineous marriages, and have a premarital or pre-pregnancy SMA test or a large panel of carrier screning tests that include major rare diseases, including SMA.

07.08.2023

Prof. Dr. Duran Canatan

Pediatrik Hematoloji ve Genetik Uzmanı

Özel Antalya Genetik Hastalıklar Değerlendirme Merkezi Mesul Müdürü