What Is Huntington Disease?

Huntington disease is a rare condition that causes parts of the brain to break down, or degenerate. It is also called Huntington chorea. The disease causes rapid, jerky body movements and the loss of mental skills (dementia). Huntington disease can cause personality changes, behaviour problems, and memory loss. Symptoms usually develop after age 40. There is no known cure. But treatment with medicines may help control the involuntary movements and behaviour changes.

Huntington disease is caused by a change, or mutation, in a gene. If you have a parent with the disease, you have a 50% chance of getting the changed gene and the disease. But there is no way to know when you will develop Huntington disease. Some people may pass on the changed gene to a child before knowing that they themselves have the changed gene.

A blood test can show whether you have the changed gene. Genetic counselling is important if you are thinking of having the test. If you have symptoms of Huntington disease, genetic counselling may be provided by your healthcare provider, such as a neurologist. If you do not have symptoms of Huntington disease, you will be referred to a medical genetics clinic for counselling. Medical geneticists and genetic counsellors are experts who can explain what the test means, tell you the benefits and risks of the test, and answer your questions. But you make the decision about whether to have the test.

What Is the Test?

The Huntington genetic test is a blood test to check for the genetic disease. If you have a family member who has Huntington disease, their blood usually is tested first to identify the changed gene that might run in your family. Then you give a blood sample, which is screened for the gene change. Testing another family member also may be important in case your family's DNA is unusual in some way that might affect the test result.

Is the Test Accurate?

Although the Huntington genetic test is highly reliable, no test is 100% accurate. Also, if you test positive, the test can't tell you when you will develop Huntington disease or how quickly the disease will advance.

Should You Be Tested?

The decision to take the test for Huntington disease is personal. You may have emotional, financial, and family reasons for taking or not taking the test.

You might choose to be tested because:

• You want to know whether you will get the disease so you can prepare yourself and your family if your test is positive. You might choose, for example, to set up financial arrangements in a certain way or change other life plans.
• You want to know because the results may affect your plans for marriage and children.
• You think the anxiety of not knowing whether you will get the disease is worse than the certainty of knowing that you will get it.
• Your provincial health plan or private insurance will pay for all or most of the test. Or, you can afford to pay for the test yourself.

You might choose not to be tested because:

• You do not want to know if you have the changed gene. You prefer to live without knowing whether you will someday get Huntington disease.
• You are concerned about how the results would affect your relationships.
  • If you test negative (you do not have the changed gene), you may feel guilty if your brother, sister, or child tests positive.
  • Or you may feel angry if you test positive and your relatives do not.
• The test is expensive, and your provincial health plan or private insurance will not pay for it.
• You are concerned that test results could affect your job options or the cost or how easily you can get private insurance. In Canada, there is a law called the Genetic Non-Discrimination Act (GNA) that protects your genetic information.
  • For more information on the risks of genetic discrimination in Canada, talk with your doctor. You can also visit the website of the Canadian Coalition for Genetic Fairness at www.ccgf-cceg.ca or call 1-800-998-7398.
• You think there is no point in knowing now because there would be nothing you could do with lifestyle or treatment to prevent the disease.