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Spinal muscular atrophy (SMA) is a neuromuscular disorder characterised by degeneration of the anterior horn cells of the spinal cord, leading to symmetrical muscle weakness and atrophy. SMA is usually divided into four clinical groups based on age of onset and maximum function obtained1. It is the second most common lethal autosomal recessive disorder in Caucasians, after cystic fibrosis, with the estimated incidence of 1:6,000-1:10,000 in newborns, and incidence in Latvia is estimated at one out of 9091 newborns2.
In pathogenesis of SMA are involved two genes, SMN1 and SMN2, from which homozygote deletion of the SMN1 gene is associated with disease development, while changes in the SMN2 gene may affect the course of the disease. In 95-98% of SMA patients’ homozygous deletion of exon 7 in SMN1 gene is found, rarely small allelic variants or deletions of exons 1 – 6 are found in SMN1 gene. Changes in this gene are found on average in 1 out of 50 people in the population, depending on ethnicity. The majority of heterozygous carriers of the deletion of SMN1 gene can be determined using methods that determine exon 7 deletion. One of the most precise methods for heterozygote testing is MLPA (Multiplex Ligation Probe amplification), which can detect large SMN1 gene deletions responsible for the development of the syndrome.
Genetic centre iVF Riga offers SMN1 and SMN2 deletion carrier testing with MLPA.
1OMIM # 253300, # 253550, # 253400, # 271150.
2Šetlere S., Strautmanis J., Rozentāls G., Ozoliņa G., Berķe L., Mičule I. “Clinical epidemiological characteristics of spinal muscle atrophy in Latvia” RSU Science conference 2018, Riga, Latvia.