Spinal muscular atrophy: Clinical validation of a single-tube multiplex real time PCR assay for determination of SMN1 and SMN2 copy numbers

► Spinal muscular atrophy (SMA) is caused mainly by absence of the SMN1 gene. ► In SMA, copy number of SMN2, a gene with reduced function, can influence severity. ► We describe a single-tube technique to estimate SMN1 and SMN2 copy number. ► In this, SMN1, SMN2 and a control gene, CFTR, are quantified by real-time PCR. ► In >1200 samples, the technique was accurate, fast, economical and reproducible.