SMN1 and proximal spinal muscular atrophy: Spinal muscular atrophy (SMA) is a neuromuscular genetic disorder characterized by progressive anterior horn motor neuron loss in the spinal cord and subsequent progressive weakness and disability.(1) The most common form of SMA, 5q-SMA, is an autosomal recessive disorder caused by homozygous pathogenic variants of the survival motor neuron 1 (SMN1) gene on chromosome 5q13.2, with an incidence of 1:6,000-1:10,000.(2,3) Before the emergence of treatments modifying the natural history of the disease, 5q-SMA was considered one of the most devastating childhood neurological diseases.