title: Homozygous SMN2 deletion is a major risk factor among twenty-five Korean sporadic amyotrophic lateral sclerosis patients.
abstract: OBJECTIVE
  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.
  
  
  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).
  
  
  CONCLUSIONS
  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.
authors.affiliation: Department of Neurology, Gangnam Severance Hospital, Brain Korea 21 Project for Medical Science, Yonsei University College of Medicine, Seoul, Korea.
authors.forename: Jun-Beom
authors.initials: JB
authors.lastname: Lee
authors.forename: Kyung-A
authors.initials: KA
authors.lastname: Lee
authors.forename: Ji-Man
authors.initials: JM
authors.lastname: Hong
authors.forename: Gyoung-Im
authors.initials: GI
authors.lastname: Suh
authors.forename: Young-Chul
authors.initials: YC
authors.lastname: Choi
mesh_terms: D000293:Adolescent; D000328:Adult; D017668:Age of Onset; D000690:Amyotrophic Lateral Sclerosis / Q000453:epidemiology* / Q000235:genetics*; D044466:Asian People / Q000235:genetics* / Q000706:statistics & numerical data*; D017353:Gene Deletion; D006720:Homozygote; D006801:Humans; D008875:Middle Aged; D056910:Republic of Korea / Q000453:epidemiology; D012307:Risk Factors; D055540:Survival of Motor Neuron 2 Protein / Q000235:genetics; D055815:Young Adult
chemical_list: C526477:SMN2 protein, human; D055540:Survival of Motor Neuron 2 Protein