Previous studies have examined blood markers such as SMN mRNA and protein levels,11 leukocyte DNA methylation profiles,11,12 and plasma proteins identified through unbiased proteomic studies.13 However, these markers lacked clear differentiation among SMA sub-types and showed limited association with disease severity, reducing their clinical utility.13 The plasma levels of neurofilament heavy chain (pNF-H)14,15 and light chain (NfL)16-19 have demonstrated potential as biomarkers for axonal damage, reflecting disease severity and treatment response in infantile-onset SMA. This evidence concerns the gene NEFL and proximal spinal muscular atrophy.