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Genetic and Rare Diseases Information Center (GARD)

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Huntington disease

Other Names for this Disease
  • HD
  • Huntington's chorea
  • Huntington's disease
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Your Question

What tests will my doctor order to confirm if I have Huntington disease?

Our Answer

We have identified the following information that we hope you find helpful. If you still have questions, please contact us.

What is Huntington disease?

Huntington disease is a progressive disorder that causes brain cell (neuron) degeneration in certain areas of the brain.  This results in uncontrolled movements, loss of intellectual abilities, and emotional disturbances. Symptoms typically appear between the ages of 35 and 44 years. People with Huntington disease most often live for 15 to 18 years after the condition appears. Huntington disease caused by mutations in the HTT gene and is inherited in an autosomal dominant manner. Each child of a person with Huntington disease has a 50 percent (1 in 2) chance of inheriting the mutation.[1] There is also a less common, early-onset from that begins in childhood or adolescence, called juvenile Huntington disease.[2]
Last updated: 6/27/2011

How is Huntington disease diagnosed?

The diagnosis of Huntington disease is suspected clinically in the presence of the following:[1]

  • Progressive motor disability featuring chorea; voluntary movement may also be affected

  • Mental disturbances including cognitive decline, changes in personality, and/or depression

  • Family history consistent with autosomal dominant inheritance

The diagnosis of Huntington disease can be confirmed through molecular genetic testing which identifies an expansion in the HD gene. A gene expansion means that the gene becomes longer as more nucleotides (the material that makes up our genes) are added. When the additional nucleotides come in sets of 3 we call them trinucleotide repeats. Huntington disease is caused by 36 or more trinucleotide repeats in the HD gene.[1][2]
Last updated: 2/25/2010

What tests will my doctor order to confirm that I have Huntington disease?

A blood test is available that can determine, in almost all cases, whether a person has the Huntington disease gene.[3] 

Confirmatory testing is used to "confirm" a neurologist's suspicion that a person has Huntington disease. It is a type of genetic testing which is often performed by a neurologist when a patient has symptoms which appear to be those generally associated with Huntington disease.[3] Using a blood sample, the genetic test analyzes DNA for the HD mutation by counting the number of repeats in the HD gene region. Individuals who do not have Huntington disease usually have 28 or fewer CAG repeats. Individuals with Huntington disease usually have 40 or more repeats.[4]

It is important to bear in mind that, even though a person may be aware that he or she has some of the symptoms associated with Huntington disease, hearing this suspicion confirmed can often have a significant psychological effect. For this reason, you are strongly encouraged to bring a support person with you to all testing sessions. You may also wish to have your testing done at an Huntington Disease Society of America (HDSA) Center of Excellence where there are resources available to guide you through the testing process.[3] To locate a Center of Excellence in your area, click here.
Last updated: 7/13/2009