Among SMA type 1 patients, the median event-free survival time with 2 SMN2 copies was much worse than that with ≥3 SMN2 copies (1.58 years vs. undefined, p < 0.05), consistent with the main opinion that more SMN2 copies were still important protective survival factors (7, 12). Here, SMN2 is linked to spinal muscular atrophy, type 1.