HDSA Center of Excellence at Hennepin County Medical Center

Genetic Testing

For researchers, finding the HD gene was only the beginning. Work is now under way to understand the gene’s function more completely so that better treatments can be designed for affected individuals. However, the discovery of the gene does have an immediate benefit in the area of genetic testing.

Any cell or tissue, including blood cells, sperm or egg cells, or fetal tissues, can be tested for the HD gene; remember, genes are present in all the cells of the body throughout life. Practically speaking, however, there are only a few situations in which genetic testing for the HD gene might be appropriate.

Diagnostic testing

Anyone with a diagnosis of HD can have "confirmation" of the diagnosis with a gene test. Confirming the diagnosis of HD is particularly important when the family history is absent or if the symptoms are unusual. Genetic counseling for other at-risk family members is very important after a diagnosis of HD is made in one individual. Remember, though, that the gene test for HD does not prove that a person’s symptoms are due to HD; it only indicates whether or not the person has the HD gene.

Predictive testing

An adult whose parent has HD might want to know, for psychological or social reasons, whether he or she has inherited the HD disease gene. This is called a "predictive" or "presymptomatic" test. At this time, there are no direct medical benefits to be gained from a predictive test. Potential benefits of knowing one’s HD gene status include relief of anxiety, improved emotional preparation for the future, and timely career, family, and financial planning.

This news has the potential to be harmful as well; some people may not be prepared to cope with the news that they have the HD gene and may become depressed. The predictive gene test may strain relationships among brothers and sisters or husbands and wife. There may be unexpected effects on employment or insurance. Some individuals who get "good news" find it difficult to cope with their new status – suddenly they have to plan for a life without HD. To ensure that patients will have a benefit from the test results, most test centers require that anyone choosing to take a predictive gene test for HD must have genetic and psychological counseling before completing the predictive test.

Many people (more than half of those at risk) do not want a predictive test. Knowing this, most centers do not test children or adults who are unable to understand and freely give consent for the test. The freedom to choose whether or not to have the test, and when to have it, is very important.

Prenatal testing

An individual affected with HD or at risk for HD may choose to have prenatal testing of a fetus for the HD gene. This can be done very early in pregnancy but should be planned before pregnancy in order to proceed smoothly. Prenatal testing is by no means the only reproductive choice for people in HD families. Some choose not to have any type of testing; other options include artificial insemination, adoption, and in vitro fertilization with preimplantation testing. Anyone affected with or at risk for HD should have genetic counseling before starting a pregnancy so that he or she can make the reproductive decisions that are right for him or her.

Special Note: We would like to acknowledge and thank the HCMC Service League for providing grant funds to help maintain these web pages.