5q-associated spinal muscular atrophy (SMA) is a rare neuromuscular disorder that is caused by loss-of-function mutations of the ubiquitously expressed survival of motor neuron 1 gene (SMN1, MIM *600,354) and is clinically characterized by progressive, proximally pronounced muscle weakness and atrophy. The gene discussed is SMN1; the disease is proximal spinal muscular atrophy.