Everyone is born with the Huntington gene, however an abnormal copy of the gene that is passed from parent to child causes the disease. Huntington’s Disease only occurs when someone is born with the abnormal gene and may then pass it on to their children. Every person who carries the abnormal gene will eventually develop symptoms if they live long enough.
In 1983 scientists discovered a gene marker linked to HD. In 1993 they isolated the gene on chromosome 4 and identified that people with HD have a mutant expanded form of the gene. A specific genetic test was developed to identify carriers of the abnormal gene. While this test is highly accurate it can’t determine when the symptoms of the disease will start or the severity of the symptoms. People can test positive for the abnormal HD gene and may remain unaffected for many years.
Should you get tested?
If you’ve been exhibiting symptoms of HD or if you have a family history of HD, then yes, testing can be used to confirm whether or not you have an abnormal Huntington’s gene.
Four recommended places in North Carolina offer genetic testing:
- The University of North Carolina at Chapel Hill.
- Duke University in Durham, North Carolina.
- Fullerton Genetics Center in Asheville, North Carolina.
- Wake Forest University Baptist Medical Center in Winston-Salem, North Carolina.
These four testing sites follow published, nationally accepted guidelines for the best and safest way to test people at risk for HD. All four places offer confirmatory testing and all of the locations except Wake Forest offer pre-symptomatic or “predictive” testing for people who aren’t displaying symptoms but want to find out if they carry the abnormal HD gene. Testing is done safely and according to stringent protocol. Your blood sample will be securely handled and results will be interpreted accurately and quickly from reputable labs, which have done thousands of tests with virtually no errors.
UNC Chapel Hill and the Fullerton Genetics Center are the only programs in North Carolina featuring certified genetic counselors who are available to speak with families specifically about HD. Many people also opt to go to UNC for testing because they are interested in information about pre-implantation genetic diagnosis (PGD), which is when an embryo created by in vitro fertilization (IVF) is tested for HD. People can opt to have their embryos tested prior to implantation so they can know for sure the embryo that is eventually implanted does not carry the gene for HD. All other options available could be discussed as well, including adoption, egg/sperm donation, CVS (chorionic villus sampling), and amniocentesis.
Genetic counseling services are also helpful to people who have already had children; it can be very helpful for a parent to speak with a genetic counselor about whether to get tested, and about how to talk to their kids about HD and what it means to be at risk of developing it.
Also, there are times when a person’s genetic test results are considered to be in the “intermediate range” and these kinds of results are always best discussed with a genetic counselor so that a person understands the implications.
Out-of-pocket costs for genetic testing of the HD gene range from $1,000–$1,200. Some of the costs may be reimbursed by insurance, although many people choose to pay out-of-pocket for reasons of confidentiality.
Many people think if they get a gene positive test result they are officially diagnosed with HD. The diagnosis of HD is actually made by a neurologist based on the presence of motor symptoms indicating HD in conjunction with a positive test result and/or positive family history of HD. So, it is possible you could get a test result that is gene positive, but the neurologist would have to be able to document the onset of symptoms in order to diagnose HD.