The diagnosis of Huntington disease can be confirmed through molecular genetic testing which identifies an expansion in the HDgene. A gene expansion means that the gene becomes longer as more nucleotides (the material that makes up our genes) are added. When the additional nucleotides come in sets of 3 we call them trinucleotide repeats. Huntington disease is caused by 36 or more trinucleotide repeats in the HD gene.
Last updated: 2/25/2010
Is genetic testing for Huntington disease available?
Testing of adults at risk for Huntington disease who have no symptoms (asymptomatic) of the disease has been available for over ten years. This type of testing is called predictive testing. Predictive testing requires careful thought, including pretest and post-test genetic counseling. This is particularly important as there is currently no cure for Huntington disease. It is also important to understand that this testing is not useful in accurately predicting the age a person found to carry a Huntington disease causing mutation will begin experiencing symptoms, the severity or type of symptoms they will experience, or rate of disease progression. However, data reported in 2004 concerning the likelihood that an individual with a particular size of trinucleotide repeats will be affected by a specific age may be useful. The Pacific Northwest Regional Genetics Group (PacNoRGG) has published a guide that can help people consider the issues around testing for HD entitled, "Testing for Huntington Disease: Making an Informed Choice"
The Division of Neurogenetics at the University of Washington is a tertiary specialty that provides clinical services to adults in the general public as well as training. They have created a booklet entitled, "Huntington Disease:Making an Informed Choice, that can be downloaded at no charge.
Orphanet lists international laboratories offering diagnostic testing for this condition. Click here and scroll down the page to learn more about the processes of certification, accreditation, and external quality assessment available to these labs. Click on Orphanet to view the list.