The average age of onset of SMA in patients with 0 copy of the NAIP gene (33.1 ± 51.98) was also less than that of patients with 1 (50.15 ± 75.81) and 2 (99 ± 96.65) copies (P < 0.0001) (Fig. 3b). The gene discussed is NAIP; the disease is proximal spinal muscular atrophy.