For those SMA patients harboring deletions of SMN1 and whose disease severities were known (n = 59), patients with higher SMN2 copy numbers (i.e., 3 or 4) had milder disease severities than those patients with fewer copies of SMN2 (i.e., 2; Fig.3B). The gene discussed is SMN2; the disease is proximal spinal muscular atrophy.