The heterozygous deletion of SMN1, exon 7 rate in black SA patients with SMA who tested negative for the homozygous SMN1, exon 7 deletion, was previously reported to be as high at 69.5%, supporting the diagnosis of SMA in these patients and suggesting that SMA is probably due to additional unidentified mutations in this region (Labrum et al., 2007). This evidence concerns the gene SMN1 and proximal spinal muscular atrophy.