In this current study, a new hybrid SMN gene sequence was identified (taaTggG) that consisted of upstream “t” and downstream “G” sequences of SMN1 and “aaTgg” sequence of SMN2. The diversity of hybrid SMN gene sequences observed in patients with SMA may be explained in part by the instability of the downstream sequence of the SMN gene. This evidence concerns the gene SMN1 and proximal spinal muscular atrophy.