- Huntington's chorea
- Huntington's disease
Your QuestionA friend of mine has been diagnosed with Huntington disease. No one else in his family has this condition. Is it possible that a chemical exposure could have caused it, such as to vinyl chloride?
We have identified the following information that we hope you find helpful. If you still have questions, please contact us.
Questions on this page
- What causes Huntington disease?
- Can people without a family history of Huntington disease still develop the condition?
- Can environmental exposures cause gene expansion like that of the CAG repeat that causes Huntington disease?
- Are there certain chemicals or substances that people with Huntington disease should avoid?
- Who can I contact to learn more about genetic disease and environmental exposure?
- How can I find a genetics professional in my area?
The HTT gene mutation that causes HD involves a DNA segment known as a CAG trinucleotide repeat. This segment is made up of three DNA building blocks that repeat multiple times in a row. The CAG segment in a normal HTT gene repeats about 10 to 35 times. In people with HD, it may repeat from 36 to over 120 times. People with 36 to 39 CAG repeats (an intermediate size) may or may not develop HD, while people with 40 or more repeats almost always develop HD.
An increased number of CAG repeats leads to an abnormally long version of the huntingtin protein. The long protein is then cut into smaller, toxic pieces that end up sticking together and accumulating in neurons. This disrupts the function of the neurons, ultimately causing the features of HD.
Freidman JH et al., Monozygotic Twins Discordant for Huntington Disease After 7 Years. Arch Neurol. 2005;62:995-997.
National Institute of Environmental Health Sciences
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Web site: http://www.niehs.nih.gov
Genetics clinics are a source of information for individuals and families regarding genetic conditions, treatment, inheritance, and genetic risks to other family members. More information about genetic consultations is available from Genetics Home Reference. To find a genetics clinic, we recommend that you contact your primary healthcare provider for a referral.
The following online resources can help you find a genetics professional in your community:
- The National Society for Genetic Counselors provides a searchable directory of US and international genetic counseling services.
- The American College of Medical Genetics has a searchable database of US genetics clinics.
- The University of Kansas Medical Center provides a list of US and international genetic centers, clinics, and departments.
- The American Society of Human Genetics maintains a database of its members, which includes individuals who live outside of the United States. Visit the link to obtain a list of the geneticists in your country, some of whom may be researchers that do not provide medical care.
- Huntington disease. Genetics Home Reference. June, 2013; http://ghr.nlm.nih.gov/condition/huntington-disease.
- Simon C Warby, Rona K Graham, and Michael R Hayden. Huntington Disease. GeneReviews. December 11, 2014; http://www.ncbi.nlm.nih.gov/books/NBK1305/.