Distal spinal muscular atrophy type 3 (DSMA3) is a rare, inherited neuromuscular disorder that affects the lower motor neurons in the spinal cord. It is caused by a mutation in the SMN2 gene, which is responsible for producing the survival motor neuron protein. Symptoms of DSMA3 include muscle weakness and wasting in the lower limbs, as well as difficulty walking and standing. In some cases, the disorder can also affect the upper limbs, leading to difficulty with fine motor skills. Treatment for DSMA3 is limited, but physical therapy and occupational therapy can help improve muscle strength and function.