Genomes Blog Post
By: Emily Larking
Huntington’s Disease is an inherited neurological illness. About 30,00 people in the United States have the disease (1). It is caused by a mutation on the HD gene, that codes for huntingtin protein production which has much more repeats than normal of a certain three-basese sequence (1). This gene is located on the fourth chromosome. It causes the degeneration of nerve cells in the brain that leads to symptoms such as changes in behavior and judgement, uncontrollable movement and physical changes such as impaired ability to swallow or speak (3).
For a predictive genetic test, the price is $200-$300. There is recommended genetic counseling that can cost up to $1,500-$2,000 (4). The most effective test is a direct-to-consumer genetic test that counts the extra repeats of the three base sequence in the Huntington gene on the fourth chromosome through a blood sample (3). The test could use a method such as the Southern Blot method. There is a very strong, almost definitive connection between the mutation in the fourth chromosome that would be tested for, and the disease.
With the direct genetic test, there is a small amount of people who have a borderline amount of repeats. Their family may be called in for genetic testing as well to get a better picture. Huntington’s can be ruled out if there are 26 or fewer repeats (3). The test can’t predict when the symptoms will start or the course of the disease (2).
There are many potential implications if the genetic testing is positive for Huntington’s Disease. There may be personal stress and possible distress to those close to the person with Huntington’s Disease. Also, Huntington’s does not have a cure. Therefore, there is no medical advantage to knowing the test results. You can only treat the symptoms as they appear. You can, however, plan for the future and factor that into any family planning decisions. The Genetic Information Non Discrimination Act (GINA) is a law that was made to stop discrimination from based on genetic information with health insurance. Although it applies to health insurance, it does not apply to life insurance so a positive test may raise prices for life insurance dramatically or may not allow for getting a policy at all. (2)
Since Huntington’s is an autosomal dominant disease, the chances of getting it if even one parent has HD will be fairly high. If both the parents have recessive alleles, the offspring will not get the disease. However, if you have two heterozygous, there’s a 75% chance of getting the disease. If one parent is heterozygous and one homozygous recessive, there’s a 50% chance. If one parent is heterozygous and one homozygous dominant, there’s a 100% chance of getting the disease. If the test is positive, the person should make a plan for the future and be prepared to address the symptoms as they come. I would recommend telling the doctor that the test was positive and ask if they have any suggestions on how to proceed.
Overall, Huntington’s Disease is an incurable disease with limited reasons to test for it. Since it is a dominant disease, there is a small chance of one developing it if it does not run through the family. Although not too complicated to test for, the consequences of a positive result outweigh the benefits in most cases.
Works Cited:
About Huntington’s Disease. (2011, November 17). Retrieved from
https://www.genome.gov/Genetic-Disorders/Huntingtons-Disease. (1)
Genetic testing and your rights. (n.d.). Retrieved from
https://hdsa.org/find-help/healthcare-and-future-planning/genetic-testing-and-your-rights/ . (2)
Huntington’s Disease: Hope Through Research. (2019, August 13). Retrieved from
https://www.ninds.nih.gov/disorders/patient-caregiver-education/hope-through-research/h
untingtons-disease-hope-through#7. (3)
Goodman, L. V. (2013, January 29). Predictive Testing for Huntington’s disease. Retrieved from
http://hddrugworks.org/dr-goodmans-blog/predictive-testing-for-huntingtons-disea. (4)