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KMID : 0391520150230020062
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Journal of the Korean Child Neurology Society
2015 Volume.23 No. 2 p.62 ~ p.66
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The Role of SMN2 Copy Number in Modulating the Spinal Muscular Atrophy Phenotype
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Woo Seung
Ko Young-Jun
Kim Soo-Yeon
Choi Sun-Ah
Yoo Il-Han
Kim Hun-Min
Lim Byung-Chan
Hwang Hee
Chae Jong-Hee
Choi Ji-Eun
Kim Ki-Joong
Hwang Yong-Seung
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Abstract
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Purpose: Spinal muscular atrophy (SMA) is degenerative disease of motor neuron caused by loss of survival motor neuron (SMN)1 gene. SMN2 gene is highly homologous to SMN1 and is known to influence disease severity according to its copy number. Our purpose was to investigate genotype-phenotype correlation between the SMN2 copy number and the clinical course in spinal muscular atrophy patients.
Methods: The correlation between SMN2 copy number and clinical severity (subtype, ventilator support, mortality and independent walking) was analyzed.
Results: The SMN2 copy number was analyzed in 60 SMA patients (male 29, female 31). The average follow-up duration was 4.0 years (0.2 to 16.7). One patient had 1 SMN2 copy and was on ventilator support. In 20 patients who had 2 SMN2 copies, 19 (95.0%) were type I and 11 (55.0%) were on ventilator support. There were 4 mortalities in these patients. In 37 patients who had 3 SMN2 copies, 36 (97.3%) were type II. The 3 patients (8.1%) were on ventilator support and 17 (45.9%) could walk independently. The two patients had 4 SMN2 copies, each patient was type I and III. Two SMN2 copies were significantly correlated with earlier ventilator dependence and higher mortality than three SMN2 copies.
Conclusion: This is the first report that compared the relationship between SMN2 copy number and clinical phenotype in Korean SMA patients. The lower SMN2 gene copies were significantly correlated with severe clinical outcomes of SMA. However, additional biomarkers capable of predicting more detailed clinical outcomes within subtypes need to be further determined in an extended cohort.
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KEYWORD
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Spinal Muscular Atrophies of Childhood, SMN2 copy number, SMA
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