Multifocal motor neuropathy (MMN) is a rare, progressive, autoimmune disease of the nerves of the muscles. MMN usually develops slowly, resulting in asymmetrical weakness of the limbs, usually without numbness, tingling, or pain. Patients with MMN can also experience fasciculations (small, involuntary muscle twitches under the skin). MMN is not fatal and does not diminish life expectancy, but it is a chronic condition without remission. Treatment can limit the progression and improve function, however. Many patients, once undergoing treatment, only experience mild symptoms over prolonged periods. Nevertheless, MMN can lead to significant disability, with loss of function in hands affecting the ability to work and perform everyday tasks, and foot drop making it hard to stand and walk. Some patients progress to the point of using mobility assistance devices such as canes, splints, and walkers.