“Huntington’s disease causes nerve cells in the brain to decay over time.  The disease affects a person’s movements, thinking ability and mental health. Huntington’s disease is rare. It’s often passed down through a changed  gene from a parent. Huntington’s disease symptoms can develop at any time, but they often begin when people are in their 30s or 40s. If the disease develops before age 20, it’s called juvenile Huntington’s disease.”

MAYO CLINIC