SMN2 and proximal spinal muscular atrophy: Before the US Food and Drug Administration’s (FDA’s)approval of the antisense oligonucleotide nusinersen in 2016 (10), adeno-associated virus serotype 9–mediated SMN1 gene replacement therapy onasemnogene abeparvovec-xioi in 2019 (11), and small molecule splicing SMN2 modifier risdiplam in 2020 (12), SMA was invariably fatal in infancy for the most severe forms of SMA.