SMA is an autosomal recessive neuromuscular disorder resulting from homozygous deletions and/or mutations of the Survival Motor Neuron 1 (SMN1) gene on Chromosome 5 (Darras et al., 2017; Lefebvre et al., 1995; Markowitz et al., 2012; Yeo & Darras, 2020). Here, SMN1 is linked to proximal spinal muscular atrophy.