Huntington's disease is a genetic neurodegenerative disorder that causes uncontrolled movements, emotional issues, and loss of cognitive abilities. It is caused by an expanded CAG repeat in the Huntington gene on chromosome 4. Symptoms typically appear in mid-life and include jerking movements, mood swings, and cognitive decline. There is no cure for Huntington's disease and treatment aims to manage symptoms, though the condition steadily worsens over time.