Monarch Disease Ontology term MONDO_0010056 (spinal muscular atrophy, type IV) can be described as follows. Proximal spinal muscular atrophy type 4 (SMA4) is the adult-onset form of proximal spinal muscular atrophy characterized by muscle weakness and hypotonia resulting from the degeneration and loss of the lower motor neurons in the spinal cord and the brain stem nuclei. Also known as: SMA type 4, SMA type IV, SMA-IV, SMA4, adult spinal muscular atrophy, spinal muscular atrophy of adults, spinal muscular atrophy, adult form, spinal muscular atrophy-4.