Spinal muscular atrophy (SMA) is a rare genetic, neuromuscular disease (incidence of 1:6,000–1:10,000 births/year) characterized by the degeneration of alpha motor neurons in the spinal cord caused by the loss or dysfunction of the SMN-1 gene 5q11-q13 (1). The gene discussed is SMN1; the disease is proximal spinal muscular atrophy.