The SMN2 gene, which shares high homology with SMN1, plays a contributory role in the pathogenesis of SMA since it can occasionally retain exon 7 during transcription, resulting in the production of full-length SMN protein that partially compensates for the deficits caused by SMN1 mutations (1–3, 5). This evidence concerns the gene SMN2 and proximal spinal muscular atrophy.