Huntington disease is a progressive brain disorder characterized by uncontrolled movements, emotional problems, and cognitive decline. The most common form, adult-onset Huntington disease, typically appears in the thirties or forties, with early symptoms including irritability, depression, small involuntary movements, poor coordination, and difficulty learning new information. As the disease progresses, affected individuals may experience more severe movements, walking, speaking, and swallowing difficulties, along with personality changes and declining cognitive abilities. The adult-onset form usually lasts 15 to 20 years after symptoms begin. A less common juvenile form of Huntington disease begins in childhood or adolescence, involving similar movement and mental changes. It progresses more quickly, with affected individuals living 10 to 15 years after symptoms appear. The disease affects about 3 to 7 per 100,000 people of European ancestry, less frequently in other populations. The disorder is caused by mutations in the *HTT* gene, which produces a protein called huntingtin. The mutation involves an abnormally long CAG trinucleotide repeat, leading to toxic protein fragments that accumulate and disrupt brain function. Huntington disease follows an autosomal dominant inheritance pattern, with the size of the CAG repeat often increasing over generations, a phenomenon known as anticipation. Individuals with 27 to 35 CAG repeats are not typically affected but are at risk of passing the disorder to their children. Diagnosis and management involve genetic testing, clinical assessments, and support from patient advocacy groups. Research and resources are available from various health organizations and databases.Huntington disease is a progressive brain disorder characterized by uncontrolled movements, emotional problems, and cognitive decline. The most common form, adult-onset Huntington disease, typically appears in the thirties or forties, with early symptoms including irritability, depression, small involuntary movements, poor coordination, and difficulty learning new information. As the disease progresses, affected individuals may experience more severe movements, walking, speaking, and swallowing difficulties, along with personality changes and declining cognitive abilities. The adult-onset form usually lasts 15 to 20 years after symptoms begin. A less common juvenile form of Huntington disease begins in childhood or adolescence, involving similar movement and mental changes. It progresses more quickly, with affected individuals living 10 to 15 years after symptoms appear. The disease affects about 3 to 7 per 100,000 people of European ancestry, less frequently in other populations. The disorder is caused by mutations in the *HTT* gene, which produces a protein called huntingtin. The mutation involves an abnormally long CAG trinucleotide repeat, leading to toxic protein fragments that accumulate and disrupt brain function. Huntington disease follows an autosomal dominant inheritance pattern, with the size of the CAG repeat often increasing over generations, a phenomenon known as anticipation. Individuals with 27 to 35 CAG repeats are not typically affected but are at risk of passing the disorder to their children. Diagnosis and management involve genetic testing, clinical assessments, and support from patient advocacy groups. Research and resources are available from various health organizations and databases.