SMN2 and proximal spinal muscular atrophy: Similarly, higher CSF levels of TNF-α and IL-17F distinguished SMA patients with two copies of SMN2 from patients with four copies (p = 0.009 and p = 0.035, respectively), and patients with three copies of SMN2 from patients with four copies (p = 0.047 and p = 0.060, respectively).