SMN2 and proximal spinal muscular atrophy: Three disease-modifying therapies (DMTs) are currently approved for the treatment of SMA: nusinersen (SPINRAZA®), an intrathecally administered antisense oligonucleotide that alters the splicing of SMN2 pre-mRNA [3, 4]; onasemnogene abeparvovec (ZOLGENSMA®), an intravenously administered gene therapy designed to deliver a functional copy of the SMN1 gene into motor neurons [5, 6]; and risdiplam (EVRYSDI®), an orally administered small molecule designed to selectively modify splicing of SMN2 pre-mRNA and promote inclusion of exon 7 thus increasing levels of functional SMN protein [7, 8].