Spinal muscular atrophy (SMA) is an autosomal recessive neurodegenerative disorder caused by mutations in the survival motor neuron 1 (SMN1) gene, which is located in the 5q13 region of chromosome 5, leading predominantly to the loss of lower motor neurons and cranial nerve nuclei in the brainstem, and resulting in progressive muscle weakness and atrophy (1–3). The gene discussed is SMN1; the disease is proximal spinal muscular atrophy.