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Huntington’s disease

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Types of brain disorders

Huntington’s disease

Huntington's disease is a neurodegenerative genetic disorder that affects muscle coordination and leads to cognitive decline and dementia.

Huntington's disease (HD) is the most common genetic cause of abnormal involuntary writhing movements called chorea (the disease used to be called Huntington's chorea). It is much more common in people of Western European descent than in those of Asian or African ancestry, and usually becomes noticeable in middle age. 


Cause of Huntington's disease

The disease is caused by a mutation on either of an individual's two copies of a gene called Huntingtin. This means any child of an affected parent has a 50% risk of inheriting the disease. In the rare situations where both parents have an affected copy, the risk increases to 75%, and when either parent has two affected copies, the risk is 100%  - all children will be affected.


The Huntingtin gene normally provides the genetic information for a protein that is also called "Huntingtin". The mutation of the Huntingtin gene codes for a different form of the protein, whose presence results in gradual damage to specific areas of the brain. The exact way this happens is not fully understood.


Symptoms of Huntington's disease

Physical symptoms can begin at any age but it's mostly commonly between 35 and 44 years of age. About six percent of cases start before the age of 21 years. 


Symptoms  vary between individuals, but the earliest symptoms are a general lack of coordination and an unsteady gait. As the disease advances, uncoordinated, jerky body movements become more apparent, along with a decline in mental abilities and behavioural and psychiatric problems. Physical abilities are gradually impeded until coordinated movement becomes very difficult.


Mental abilities generally decline into dementia. Complications such as pneumonia, heart disease, and physical injury from falls reduce life expectancy to around twenty years after symptoms begin. There is no cure, and full-time care is required in the later stages of the disease. Emerging treatments can relieve some of its symptoms.


Genetic testing for Huntington's disease

Genetic testing can be performed at any stage of development, even before the onset of symptoms. This fact raises several ethical debates:

  • what age is  considered mature enough for someone to choose testing
  • should parents have the right to have their children tested
  • managing confidentiality and disclosure of test results.


Genetic counseling has developed to inform and aid individuals considering genetic testing, and has become a model for other genetically dominant diseases.


Research into Huntington's disease

Self-help support organizations, first founded in the 1960s and increasing in number, have been working to increase public awareness, to provide support for individuals and their families, and to promote research. The Hereditary Disease Foundation, a research group born out of the first support organization, was instrumental in finding the gene in 1993.


Since that time, many new research discoveries have been made and understanding of the disease is improving. Current research directions include determining the exact mechanism of the disease, improving animal models to expedite research, clinical trials of pharmaceuticals to treat symptoms or slow the progression of the disease, and studying procedures such as stem cell therapy with the goal of repairing damage caused by the disease.   


References and further information

This information has been adapted from pages on Wikipedia at under the GNU Free Licence Agreement.


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