SMN2 and proximal spinal muscular atrophy: The breakthrough in SMA therapy came with the approval of an antisense oligonucleotide Nusinersen (Spinraza®, Biogen, Cambridge, MA, USA) targeting SMN2 [8], followed by the SMN1 gene replacement therapy (Zolgensma®, AveXis, Inc., Basel, Switzerland) [10] and a small molecule for correction of the SMN2 splicing defect (EvrysdiTM, Genentech USA, Inc., South San Francisco, CA, USA) [9].