Schoser and colleagues, using immunohistochemistry on muscle biopsies from a small cohort (n = 5) of patients with ALS, spinal muscular atrophy, and chronic axonal neuropathies, observed strong MMP-9 immunoreactivity—and to a lesser extent, MMP-2 and MMP-7—in all samples [39]. Here, MMP2 is linked to proximal spinal muscular atrophy.