Huntington's disease is a genetic disorder that causes brain cells to waste away over time. It is passed down through families and results from a defective gene on chromosome 4 that causes an excess of the protein CAG. The disease has two types - adult onset which occurs in one's 30s-40s and is more common, and childhood onset which happens at a young age in rare cases. Signs and symptoms include involuntary movements, cognitive and psychiatric problems, and eventually death around 15-20 years after diagnosis usually from infection or sometimes suicide.