Taken together with the evidence on NFs, it is likely that neurodegenerative markers in general might reflect treatment response in SMA patients, but more data derived from bigger cohorts are needed to prove this hypothesis for tau protein, ß-amyloid peptides, and cathepsin D, and possibly other molecules not yet identified until now (see Table 4). The gene discussed is CTSD; the disease is proximal spinal muscular atrophy.