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Diseases

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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Overview



What is Huntington disease?

What causes Huntington disease?

How is Huntington disease inherited?

Is genetic testing for Huntington disease available?

How is Huntington disease diagnosed?

How might Huntington disease be treated? Can it be cured?


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

What causes 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 likely plays an important role in nerve cells.[3]

The type of mutation in the HTT gene that causes Huntington disease is called a CAG repeat expansion. CAG repeats are segments of DNA that are normally repeated 10 to 35 times. In people with Huntington disease the CAG segment is repeated 36 to more than 120 times. The abnormally expanded CAG segment leads to the production of a huntingtin protein that contains a long stretch of the amino acid glutamine. The elongated protein disrupts the normal function of nerve cells in certain parts of the brain, and ultimately leads to the death of those cells. The dysfunction and loss of nerve cells cause the signs and symptoms of Huntington disease.[3]
Last updated: 2/25/2010

How is Huntington disease inherited?

Huntington disease is inherited in an autosomal dominant manner. This means that one copy of the altered gene in each cell is sufficient to cause the disorder. Click here to learn more about autosomal dominant inheritance. 
Last updated: 2/25/2010

Is genetic testing for Huntington disease available?

Testing of adults at risk for Huntington disease who have no symptoms (asymptomatic) of the disease has been available for over ten years. This type of testing is called predictive testing. Predictive testing requires careful thought, including pretest and post-test genetic counseling. This is particularly important as there is currently no cure for Huntington disease. It is also important to understand that this testing is not useful in accurately predicting the age a person found to carry a Huntington disease causing mutation will begin experiencing symptoms, the severity or type of symptoms they will experience, or rate of disease progression. However, data reported in 2004 concerning the likelihood that an individual with a particular size of trinucleotide repeats will be affected by a specific age may be useful.[1][2]  The Pacific Northwest Regional Genetics Group (PacNoRGG) has published a guide that can help people consider the issues around testing for HD entitled, "Testing for Huntington Disease: Making an Informed Choice"
Last updated: 2/25/2010

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

How might Huntington disease be treated? Can it be cured?

Scientists are trying to understand what the gene mutation actually does to structures in the brain and how it affects the rest of the body.  Therefore, there is no cure for Huntington disease and there is still no known way to stop the disease from getting worse. The goal of treatment is to slow down the course of the disease and help the person function for as long and as comfortably as possible.[4]

The Huntington Disease Society of America (HDSA) Centers of Excellence for Family Services Program helps to create regional Centers that offer clinical care and services for individuals affected by HD and their families. HDSA Centers of Excellence provide comprehensive services through a multidisciplinary health care team. To find a center in your area, you can contact the HDSA organization at (800) 345-HDSA (4372) or click here to go directly to their Web site.

Caregivers for individuals with Huntington disease can find a list of resources on the HDSA Web site at the following link:
http://www.hdsa.org/living-with-huntingtons/family-care/caregivers.html
Last updated: 3/2/2010

References
  1. Warby SC, Graham RK &Hayden MR. Huntington Disease. GeneReviews. April 2010; http://www.ncbi.nlm.nih.gov/books/NBK1305/. Accessed 2/4/2014.
  2. Huntington disease . Genetics Home Reference. OCtober 2008; http://ghr.nlm.nih.gov/condition/huntington-disease . Accessed 6/27/2011.
  3. Huntington disease. Genetics Home Reference. 2013; http://ghr.nlm.nih.gov/condition=huntingtondisease. Accessed 2/4/2014.
  4. Huntington Disease. MEDLINEplus. http://www.nlm.nih.gov/medlineplus/huntingtonsdisease.html. Accessed 1/1/1900.