� Brief Communication∙Diagnostic Genetics � Determination of SMN1 and SMN2 Copy Numbers in a Korean Population using Multiplex Ligation-dependent Probe Amplification

Spinal muscular atrophy (SMA), a disease character-ized by the degeneration of the anterior horn cells of the spinal cord, causes symmetric proximal muscle weakness. Inapproximately 95 % of cases, SMA is caused by the homo-zygous deletion of the survival motor neuron 1 (SMN1) gene (5q13) or its conversion to SMN2 [1]. The prevalence of SMA, an autosomal recessive disease, is approximately 1 in 10,000 newborns [2]. Hendrickson et al. [3] reported that the carrier frequency of SMN mutation was different amongdifferent ethnic groups in North America: the car-rier frequency was 2.7 % in Caucasians, 1.8 % in Asians, 1.1 % in African Americans, and 0.8 % in Hispanics. The carrier frequency of the later 2 groups was lower than that of the former groups. Copy number analysis of the SMN1 gene is important to identify carriers with SMNmu-tation. The American College of Medical Genetics (ACMG) recommends universal screening for the presence of SMA mutation to identify carriers because this condition is as