Spinal Muscular Atrophy (SMA) is clinically characterized by progressive muscle weakness depending upon the degeneration in the anterior horn cells of spinal cord and cranial nerve nuclei.
SMN gene causing the disease is localized at the long arm of (5q13) of chromosome 5. Around 95-98 % of patients have homozygous deletions at exons 7and 8 regions of SMN-1 gene. For about 2-5 % of the patients a compound heterozygosity at exons 7 and 8 or point mutations are detected.