Yonsei Med J.  2012 Jan;53(1):53-57. 10.3349/ymj.2012.53.1.53.

Homozygous SMN2 Deletion is a Major Risk Factor among Twenty-Five Korean Sporadic Amyotrophic Lateral Sclerosis Patients

• Lee JB
• Lee KA
• Hong JM
• Suh GI
• Choi YC

• KMID: 1779686
• DOI: http://doi.org/10.3349/ymj.2012.53.1.53

Abstract

PURPOSE
The association between survivor motor neuron (SMN) gene deletion and spinal muscular atrophy suggests that sporadic amyotrophic lateral sclerosis (sALS) may be related to SMN deletion. We examined the association between the SMN genotype and susceptibility to and severity of sALS.
MATERIALS AND METHODS
We genotyped the copy number of SMN1 and SMN2 in 25 patients diagnosed with sporadic ALS and 100 healthy subjects in a Korean population. Onset age and medical research council (MRC) scale were compared among patients according to SMN1 : SMN2 genotypes.
RESULTS
There was a significantly higher incidence of homozygous deletion of SMN2 (SMN1 : SMN2 genotype, 2 : 0) in sALS patients (20%) than in the normal controls (2%) (p<0.001). The onset age for patients with homozygous deletion of SMN2 (2 : 0) was significantly younger (34+/-15.38 years) than that of patients with 2 : 1, 2 : 2 and 2 : 3 of the SMN1 : SMN2 genotype (59.5+/-5.09; 52.69+/-16.46 and 50+/-0.00 years) (p=0.049). The ratio of patients with an MRC scale above G4- was smaller in the 2 : 0 genotype (40%) than in the 2 : 1, 2 : 2 and 2 : 3 genotypes (83.3%, 100% and 100%) (p=0.02).
CONCLUSION
The homozygous SMN2 deletion (2 : 0) was statistically more frequent and associated with earlier onset age and lower MRC scale in Korean sALS patients. These suggest that SMN2 deletion may be one of the factors associated with susceptibility to and severity of sALS in a Korean population.

Keyword

SMN1; SMN2; amyotrophic lateral sclerosis; age of onset; disease susceptibility; severity of illness index

MeSH Terms

Adolescent
Adult
Age of Onset
Amyotrophic Lateral Sclerosis/*epidemiology/*genetics
Asian Continental Ancestry Group/*genetics/*statistics & numerical data
Gene Deletion
Homozygote
Humans
Middle Aged
Republic of Korea/epidemiology
Risk Factors
Survival of Motor Neuron 2 Protein/genetics
Young Adult

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