In our discovery cohort, ten pediatric SMA patients with an age range between 3 weeks and 6.5 years at start of treatment were included: 40% (n = 4) of all patients had two SMN2 copies, 50% (n = 5) had three SMN2 copies and 10% (n = 1) had four SMN2 copies. This evidence concerns the gene SMN2 and proximal spinal muscular atrophy.