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Spinal muscular atrophy (SMA) is an autosomal recessive disease and characterized by symmetrical muscle weakness. All types of SMA are the result of mutations in survival motor neuron (SMN1) gene. Although, mutations in SMN1 gene are essential for pathogenesis of the disease, copy number variation in SMN2 are related to the age of onset and the severity of disease. The most common mutation on the SMN1 is homozygous deletion of exon 7 that is seen in 95%-98% of patients, followed by compound heterozygous for a deletion of exon 7 and a point mutation in the another allele of SMN1 which is seen in 2%-5% of cases. SMA patients with homozygous point mutation in SMN1 gene reported very rarely.