This book describes Huntington’s disease (HD), a rare neurodegenerative genetic disorder that causes a triad of motor, cognitive, and psychiatric/behavioral symptoms and affects about 6 in 100,000 people worldwide. Although the age of onset of HD symptoms is usually 30 to 50 years, a rare juvenile-onset form of HD also occurs. The autosomal dominant pattern of inheritance followed by HD is illustrated in the book with pedigree scenarios. The author details how mutations in the HTT gene on chromosome 4 cause HD and how a genetic test can be used by people who might have inherited adult-onset HD and couples who are at risk for passing HD on to their children. The book describes the available treatments for HD and presents new approaches such as experimental drugs, stem cell therapy, and gene therapy that might be able to effectively treat or even cure HD.