Amyotrophic lateral sclerosis, uh my uh TROF ihk LAT uhr uhl sklih ROH sihs, also called ALS, is a rare, incurable disease of the nervous system. It is also called Lou Gehrig's disease, after a baseball player who died from it. ALS gradually destroys the nerves that control the muscles. Weakness, paralysis, and eventually death result. Physicians advise patients to remain active as long as possible. No treatment can halt ALS.