While subsequent studies have ruled out its direct responsibility, for this disease [17, 22], NAIP has however shown to be more frequently mutated in SMA affected patients than in general population, with homozygous deletions in 45–67% of typeI and 20–42% of typeII/typeIII SMA patients [12, 20, 23–25]. The gene discussed is NAIP; the disease is proximal spinal muscular atrophy.