NAIP and proximal spinal muscular atrophy: This is in consistence with several studies which have reported that loss of both copies of NAIP is not sufficient to cause the disease, as 1–2% of unaffected individuals and 2% of carrier parents, showed deleted NAIP gene in both chromosomes have found that in their SMA patients, deletion of NAIP gene was always associated with homozygous deletions of SMN1 gene.