In 1994, the association between the survival motor neuron 1 (SMN1) gene and SMA was reported in the 5q13.2 region after defining the exact chromosomal location of the gene.2Exon 7/8homozygous deletion in theSMN1gene was detected in 95 to 98% of SMA patients, and point mutations in this gene were detected in 2 to 5% of patients.3Exon 7/8 homozygous deletion in theSMN1gene is the main factor in the diagnosis of SMA. The gene discussed is SMN1; the disease is proximal spinal muscular atrophy.