Regarding the issues with SMA-NBS, no method for finding SMA patients with compound heterozygous abnormalities involving unilateral allelic deletion and unilateral allelic point mutation of SMN1 (which is seen in approximately 5% of SMA patients), which are not targeted by current SMA-NBS testing, has yet been established. This evidence concerns the gene SMN1 and proximal spinal muscular atrophy.