NAIP and proximal spinal muscular atrophy: There was a much lower survival rate of patients with a homozygous deletion in one or two exons compared with patients without a deletion (p < 0.05), but there was no significant difference between patients with a homozygous deletion in one exon and those with a homozygous deletion in exon 4 and 5 of NAIP in Type I SMA patients.