Huntington's Disease (HD)

Huntington's Disease

Diagnosis

Genetic Testing for Huntington's Disease

Huntington Disease is an autosomal dominant disease. Individuals have two copies of each gene, one gene inherited from the mother, and one gene inherited from the father. In autosomal dominant diseases, only one copy of the mutated or changed gene is sufficient to result in expression of the disease. Each child of an affected parent has a 50% chance of inheriting the gene that causes the disease and developing symptoms of the disease during the normal lifespan. If a child does not inherit the disease causing gene, the child will not develop symptoms of HD nor will that child transmit the gene that causes HD to future generations. HD affects males and females with equal frequency.

Presymptomatic genetic testing is for individuals at risk for HD who do not have symptoms. Presymptomatic genetic testing involves genetic counseling. The Huntington Disease Society of America has published recommended guidelines for presymptomatic genetic testing. In general, the guidelines recommend pre- and post-test counseling be incorporated in any pre-symptomatic testing program.

The testing program should include the following components:

Initial telephone contact/pre-screening interview
Three pre-test, in-person sessions for genetic counseling, neurological evaluation and psychological evaluation
Fourth session for disclosure of results and post-test counseling

The goal of this counseling process is to ensure the person seeking genetic testing understands the implications of the test and is prepared to know the results.

Confirmatory genetic testing determines whether individuals showing symptoms actually have the HD gene. Genetic testing for individuals with symptoms may be necessary if the family history of the HD is uncertain.

The requirements for the diagnose of HD include...

Medical history
Family history
Neurological examination
Brain imaging test (MRI, CT)
Laboratory tests
Genetic test (if necessary)

Confirmatory testing may be offered to an individual with clear symptoms of HD and a documented family history. However, a clinical neurological examination remains the definitive means of diagnosis.

In 1979, a research roster of Huntington's disease patients and families was established at Indiana University. The HD research roster computerizes the names of families, including information about the history of HD in the family and other related data. This information identifies families who are interested in participating in research projects. The Huntington's Disease Research Roster provides an opportunity for families to store DNA from persons who are presumed to have HD. Storing DNA will later assist in confirming the diagnosis of HD in the family. For more information on DNA banking and the Huntington's Disease Research Roster call (317) 274-5744 or e-mail slcraig@iupui.edu.