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GENOTYPIC AND PHENOTYPIC CHARACTERISTICS OF PATIENTS WITH SPINAL MUSCULAR ATROPHY AT VIETNAM NATIONAL CHILDREN'S HOSPITAL
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Abstract
Spinal muscular atrophy (SMA) is an autosomal recessive neuromuscular disorder caused by mutations in the survival motor neuron (SMN) gene, with the severity influenced by the number of SMN2 gene copies. Objective: To characterize the SMN1 and SMN2 genotypes and the correlation between genotype and phenotype. Method: This cross-sectional descriptive study was conducted on 22 children with SMA, analyzing their SMN1 and SMN2 genes using PCR, MLPA, and gene sequencing techniques. Results: Twenty-one children had a homozygous genotype with a deletion of exon 7 in the SMN1 gene. One patient had a complex heterozygous genotype with a deletion of exons 7 and 8 in one SMN1 copy and a complex mutation involving a small fragment deletion along with a small fragment insertion in the other SMN1 copy c.156-165delinsCA (p. Ala53LysfsX3). Regarding the SMN2 gene, 20 patients had 3 copies, one had 1 copy, and one had 4 copies. All patients with 3 or 4 copies of the SMN2 gene displayed the SMA II phenotype, while those with two copies of the SMN2 gene exhibited the SMA I phenotype. Conclusion: Most SMA patients had a homozygous deletion of exon 7 in the SMN1 gene, and the number of SMN2 copies correlated with the phenotypic expression of SMA in pediatric patients. The patients with 2 copies of the SMN2 gene presented the SMA I phenotype, whereas patients with 3 or 4 copies of the SMN2 gene displayed the SMA II phenotype.
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Keywords
Spinal muscular atrophy, SMN1 gene, SMN2 gene
References
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