What is currently known is that SMA pups display a number of neuropathological alterations ranging from delayed NMJ maturation to NF accumulation at NMJs both in experimental models (Ling et al., 2010) and in human patients (Martínez-Hernández et al., 2013): a possible explanation for such early abnormalities could be found in an impairment of neurotrypsin/agrin system, as supported by a few evidence in literature. This evidence concerns the gene PRSS12 and proximal spinal muscular atrophy.