SMN1 and proximal spinal muscular atrophy: 5q-Spinal muscular atrophy (5q-SMA) is an autosomal-recessive neuromuscular disease with an incidence of 1:10,000, and is caused by a homozygous mutation or deletion of survival of the motor neuron 1 gene (SMN1) located on chromosome 5q, which impedes the sufficient production of SMN proteins1,2.