In Parkinson's disease (PD), the protein α-synuclein misfolds and then assembles into fibrils. These fibrils coalesce to form Lewy bodies inside of neurons.
Amyotrophic lateral sclerosis (ALS) is also known as Lou Gehrig's disease. In ALS, motor neurons degenerate and die, resulting in the inability to control muscle movement.
Huntington's disease (HD) is unique among the other neurodegenerative diseases in that it is always inherited. HD is caused by abnormal huntingtin protein.