Huntington's Disease
Huntington's disease (HD) is a progressive, neurodegenerative disorder that presents with motor disturbances, psychiatric symptoms, and cognitive decline.1 HD is inherited in an autosomal dominant manner. HD is typically an adult-onset disorder with many individuals expressing symptoms between the fourth and fifth decade of life. However, onset of symptoms can be variable, with the onset of symptoms at younger or older ages. HD is caused by an unstable CAG trinucleotide repeat expansion (referred to as HD mutation) in the IT15 gene located on chromosome 4p16.3. Pharmacologic therapy is limited to symptomatic treatment2 and presently there is no cure for HD. Athena Diagnostics, Inc. (Athena) offers diagnostic HD testing to assist physicians in confirming the clinical diagnosis of HD in an individual. In addition, Athena offers predictive HD testing to clarify the risks of those asymptomatic family members related to an individual affected with HD. Outlined below is Athena's HD testing policy.3 Diagnostic (Symptomatic) Testing:
Diagnostic testing determines whether an individual exhibiting possible symptoms of HD has an HD mutation in the IT15 gene. Athena performs HD testing for patients with symptoms of HD and a documented family history, and/or for patients with neurological symptoms that appear to be HD, but for whom there is no family history. Predictive (Asymptomatic) Testing:
Predictive testing is also referred to as asymptomatic or presymptomatic testing. Predictive testing is utilized to determine if an asymptomatic individual with a positive family history of HD has an HD mutation in the IT15 gene. To optimize the benefits of predictive testing and minimize the risks of adverse outcomes, the American Academy of Neurology (AAN) and the Huntington's Disease Society of America (HDSA) have published recommendations and practice guidelines for physicians that address many of the issues surrounding predictive testing. The HDSA recommends that individuals who request predictive testing undergo a standardized predictive testing protocol. The predictive testing protocol involves pre-test interviews whereby the reasons for requesting the test, the individual's knowledge of HD, the possible impact of positive or negative results, and neurological and psychological functioning are assessed. The HDSA also recommends post-test follow-up counseling. While Athena does not require documentation of adherence to the predictive testing protocol, Athena strongly encourages physicians to utilize the HD predictive testing protocol. Athena does require physicians to read our Athena Diagnostics' HD Presymptomatic Testing Pack as well as to complete and return the Physician's Authorization to Perform Genetic Testing form in order for predictive testing to proceed. Testing of Minors:
Athena does not perform predictive HD testing for individuals under the age of 18. In cases of diagnostic HD testing for minors, there must be medically compelling reasons for testing. Athena requires written documentation of the minor's symptoms from the referring physician and completion and return of the Physician's Authorization to Perform Genetic Testing form in order for diagnostic HD testing to proceed. Athena does not perform predictive HD testing for the purposes of adoption-related decisions or reduction of parental anxiety in the absence of clinical symptomatology.4,5 Prenatal Testing:
Athena offers prenatal HD testing and recommends that the affected or at risk parent be tested prior to prenatal testing to confirm the presence of the familial HD mutation. Athena requires completion and return of the Physician's Authorization to Perform Genetic Testing form in order for prenatal testing to proceed. Athena does not perform prenatal testing for the HD mutation after 21 weeks of pregnancy. Athena strongly encourages physicians to refer to the AAN guidelines when counseling parent(s) in the decision making process regarding whether to proceed with prenatal diagnosis.5 Questions and Follow Up
Please contact our genetic counselor, Elizabeth Couchon, or our Laboratory Director, William Seltzer, Ph.D. at 800-394-4493 for assistance with any of the following: - Questions regarding Athena's HD testing policy
- Consultation about patients that present with a compelling need for testing that is not outlined in this policy
- To find a Huntington disease testing center and/or genetic services in your area
- Any written documentation required by this policy
If you would like to request an HD Presymptomatic Testing Pack, please contact us at Athena Diagnostics 1 Brinkman RR, Meze MM, Theilmann J, Almqvist E, Hayden MR (1997) The likelihood of being affected with Huntington disease by a particular age, for a specific CAG size. Am J Hum Genet 60:1202-1210.
2 Mahbubul Huq AHM, Hayden MR (1998) Huntington Disease. www.genetests.org: p.7.
3 (2000) Massachusetts Ann. Laws ch. 111 section 70G requires laboratories performing genetic testing to obtain authorization from the medical practitioner that written informed consent has been obtained or that the testing is being ordered for the purpose of diagnosis or detecting an existing disease, illness, impairment or disorder.
4 Huntington's Disease Society of America (Abramson R, Hall W, Quaid K) (1994) Guidelines for genetic testing for Huntington's disease. New York: Huntington's Disease Society of America.
5 International Huntington Association and the World Federation of Neurology Research Group on Huntington's Chorea (1994) Guidelines for the molecular genetics predictive test in Huntington's disease. Neurology 44:1533-1536.
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