Amyotrophic lateral sclerosis (ALS), also known as motor neurone disease (MND) or Lou Gehrig's disease in the United States, is a rare, terminal neurodegenerative disorder that results in the progressive loss of both upper and lower motor neurons that normally control voluntary muscle contraction.[3] ALS is the most common form of the motor neuron diseases.[8] ALS often presents in its early stages with gradual muscle stiffness, twitches, weakness, and wasting.[3] Motor neuron loss typically continues until the abilities to eat, speak, move, and, lastly, breathe are all lost.[3] While only 15% of people with ALS also fully develop frontotemporal dementia, an estimated 50% face at least some minor difficulties with thinking and behavior.[9] Depending on which of the aforementioned symptoms develops first, ALS is classified as limb-onset (begins with weakness in the arms or legs) or bulbar-onset (begins with difficulty in speaking or swallowing).[10]

Reference
Wiki: Familial amyotrophic lateral sclerosis