Identifying and Treating HD

Genetic Testing for HD

HD Predictive Testing Program

Genetic TestingTesting for the HD gene mutation is available at the HDCRC. Participants must be 18 or older and accompanied by a support person. Our testing program provides patient education, genetic counseling, and genetic testing.

The process requires one phone screening and two on-site visits with our geneticist, neuropsychologist, and neurologist. Confidentiality is strictly maintained. Testing is offered at a reduced cost. Contact us for more detailed information.

To be tested or not to be tested?

Whether you have been aware that HD is in the family, or you are finding out for the first time, it is important to have a clear understanding of predictive testing and its impact. The decision to undergo predictive testing for the HD gene mutation is most likely one of the most difficult decisions one will face.

Some issues to consider before being tested: ability to cope with positive or negative results, relationships with family and friends, insurance planning, marriage and/or family planning, legal issues, career decisions, support system

What do my results mean?

A buccal sample will be analyzed in order to measure the size of a CAG trinucleotide repeat in the huntingtin gene on chromosome 4. Repeat sizes less than or equal to 26 are considered normal. Repeat sizes from 27 to 35 are considered normal, but could expand when passed to a child. Repeat sizes from 36 to 39 are considered abnormal with incomplete penetrance (not everyone within this range develops symptoms). Repeat sizes greater than or equal to 40 are considered abnormal with complete penetrance.

Number of CAG Repeats
Interpretation
≤26 Normal range; This individual will not develop HD.
27-35 Normal range for individual being tested; Number represents a normal mutable allele that may expand when passed to a child.
36-39 Some, but not all, individuals in this range will develop HD symptoms; The next generation is at risk.
≥40 Individual will develop symptoms; The next generation is at risk.