SMN2 and proximal spinal muscular atrophy: Even if the exact clinical expression of this novel SPG4 mutation is not yet known, altered SMN expression has already been hypothesized to play a role in ALS with quite conflicting results [6, 9, 11], starting from the original hypothesis that the lack of this gene product might induce the same well-known dysfunction that determines and modulates SMA clinical phenotype [7, 8].