Huntington disease - Genetics Home Reference

Huntington disease - Genetics Home Reference

Huntington Disease: Genetics & Recent Insights

What is Huntington disease? From the NIH Genetics Home Reference. A progressive genetic brain disorder that causes uncontrolled movements, emotional problems, and loss of thinking ability

Find out what disorders and tests are associated with Huntington disease, from the NIH Genetic Testing Registry

The Huntingtin gene: GeneCards 

The incidence and prevalence of Huntington's disease: a systematic review and meta-analysis.
Pringsheim T, et al Mov Disord. 2012 Aug;27(9):1083-91.

Huntington disease: natural history, biomarkers and prospects for therapeutics. 
Christopher A. Ross et al. Nature Reviews Neurology, March 2014

Diagnostic genetic testing for Huntington's disease 
Craufurd D, et al. Pract Neurol 2014 Aug

Thinking about the end of life: a common issue for patients with Huntington's disease 
Booij SJ, et al. J Neurol 2014 Sep

Huntington disease

On this page:

 

• Description 
• Genetic changes 
• Inheritance 
• Diagnosis 
• Additional information
• Other names 
• Glossary definitions

Reviewed June 2013

What is Huntington disease?

Huntington disease is a progressive brain disorder that causes uncontrolled movements, emotional problems, and loss of thinking ability (cognition).

Adult-onset Huntington disease, the most common form of this disorder, usually appears in a person's thirties or forties. Early signs and symptoms can include irritability, depression, small involuntary movements, poor coordination, and trouble learning new information or making decisions. Many people with Huntington disease develop involuntary jerking or twitching movements known as chorea. As the disease progresses, these movements become more pronounced. Affected individuals may have trouble walking, speaking, and swallowing. People with this disorder also experience changes in personality and a decline in thinking and reasoning abilities. Individuals with the adult-onset form of Huntington disease usually live about 15 to 20 years after signs and symptoms begin.

A less common form of Huntington disease known as the juvenile form begins in childhood or adolescence. It also involves movement problems and mental and emotional changes. Additional signs of the juvenile form include slow movements, clumsiness, frequent falling, rigidity, slurred speech, and drooling. School performance declines as thinking and reasoning abilities become impaired. Seizures occur in 30 percent to 50 percent of children with this condition. Juvenile Huntington disease tends to progress more quickly than the adult-onset form; affected individuals usually live 10 to 15 years after signs and symptoms appear.

How common is Huntington disease?

Huntington disease affects an estimated 3 to 7 per 100,000 people of European ancestry. The disorder appears to be less common in some other populations, including people of Japanese, Chinese, and African descent.

What genes are related to Huntington disease?

Mutations in the HTT gene cause Huntington disease. The HTT gene provides instructions for making a protein called huntingtin. Although the function of this protein is unknown, it appears to play an important role in nerve cells (neurons) in the brain.

The HTT mutation that causes Huntington disease involves a DNA segment known as a CAG trinucleotide repeat. This segment is made up of a series of three DNA building blocks (cytosine, adenine, and guanine) that appear multiple times in a row. Normally, the CAG segment is repeated 10 to 35 times within the gene. In people with Huntington disease, the CAG segment is repeated 36 to more than 120 times. People with 36 to 39 CAG repeats may or may not develop the signs and symptoms of Huntington disease, while people with 40 or more repeats almost always develop the disorder.

An increase in the size of the CAG segment leads to the production of an abnormally long version of the huntingtin protein. The elongated protein is cut into smaller, toxic fragments that bind together and accumulate in neurons, disrupting the normal functions of these cells. The dysfunction and eventual death of neurons in certain areas of the brain underlie the signs and symptoms of Huntington disease.

Read more about the HTT gene.

How do people inherit Huntington disease?

This condition is inherited in an autosomal dominant pattern, which means one copy of the altered gene in each cell is sufficient to cause the disorder. An affected person usually inherits the altered gene from one affected parent. In rare cases, an individual with Huntington disease does not have a parent with the disorder.

As the altered HTT gene is passed from one generation to the next, the size of the CAG trinucleotide repeat often increases in size. A larger number of repeats is usually associated with an earlier onset of signs and symptoms. This phenomenon is called anticipation. People with the adult-onset form of Huntington disease typically have 40 to 50 CAG repeats in the HTT gene, while people with the juvenile form of the disorder tend to have more than 60 CAG repeats.

Individuals who have 27 to 35 CAG repeats in the HTT gene do not develop Huntington disease, but they are at risk of having children who will develop the disorder. As the gene is passed from parent to child, the size of the CAG trinucleotide repeat may lengthen into the range associated with Huntington disease (36 repeats or more).

Where can I find information about diagnosis or management of Huntington disease?

These resources address the diagnosis or management of Huntington disease and may include treatment providers.

• Gene Review: Huntington Disease
• Genetic Testing Registry: Huntington's chorea
• Huntington's Disease Society of America: HD Care
• MedlinePlus Encyclopedia: Huntington's Disease
• University of Washington Medical Center: Testing for Huntington Disease: Making an Informed Choice

You might also find information on the diagnosis or management of Huntington disease inEducational resources and Patient support.

General information about the diagnosis and management of genetic conditions is available in the Handbook. Read more about genetic testing, particularly the difference between clinical tests and research tests.

To locate a healthcare provider, see How can I find a genetics professional in my area? in the Handbook.

Where can I find additional information about Huntington disease?

You may find the following resources about Huntington disease helpful. These materials are written for the general public.

• MedlinePlus - Health information (2 links)
• Genetic and Rare Diseases Information Center - Information about genetic conditions and rare diseases (2 links)
• Additional NIH Resources - National Institutes of Health (3 links)
• Educational resources - Information pages (11 links)
• Patient support - For patients and families (7 links)

You may also be interested in these resources, which are designed for healthcare professionals and researchers.

• Gene Reviews - Clinical summary
• Genetic Testing Registry - Repository of genetic test information (2 links)
• ClinicalTrials.gov - Linking patients to medical research
• OMIM - Genetic disorder catalog

What other names do people use for Huntington disease?

• Huntington chorea
• Huntington chronic progressive hereditary chorea
• Huntington's chorea
• Huntington's disease

For more information about naming genetic conditions, see the Genetics Home Reference Condition Naming Guidelines and How are genetic conditions and genes named? in the Handbook.

What if I still have specific questions about Huntington disease?

Ask the Genetic and Rare Diseases Information Center.

Where can I find general information about genetic conditions?

The Handbook provides basic information about genetics in clear language.

• What does it mean if a disorder seems to run in my family?
• What are the different ways in which a genetic condition can be inherited?
• If a genetic disorder runs in my family, what are the chances that my children will have the condition?
• Why are some genetic conditions more common in particular ethnic groups?

These links provide additional genetics resources that may be useful.

• Genetics and Health
• Resources for Patients and Families
• Resources for Health Professionals

What glossary definitions help with understanding Huntington disease?

adenine ; allele ; anticipation ; autosomal ; autosomal dominant ; cell ; chorea ; chronic ; cognition ;cytosine ; depression ; DNA ; gene ; guanine ; hereditary ; inherited ; involuntary ; juvenile ;mutation ; protein ; toxic ; trinucleotide repeat

You may find definitions for these and many other terms in the Genetics Home Reference Glossary.

See also Understanding Medical Terminology.

References (10 links)

The resources on this site should not be used as a substitute for professional medical care or advice. Users seeking information about a personal genetic disease, syndrome, or condition should consult with a qualified healthcare professional. See How can I find a genetics professional in my area? in the Handbook.