A group of rare, genetic, motor neuron disease characterized by childhood or adult onset progressive, predominantly proximal, muscular weakness and wasting. Included diseases are Autosomal dominant adult-onset proximal spinal muscular atrophy, Lower motor neuron syndrome with late-adult onset, and Autosomal dominant childhood-onset proximal spinal muscular atrophy. The disease or phenotype is Experimental Factor Ontology term EFO_0700051 (autosomal dominant proximal spinal muscular atrophy). Also known as: proximal spinal muscular atrophy, autosomal dominant.