Mapping of the genome vastly expanded the level of knowledge scientists have for understanding genetic disorders, including Huntington's Disease. As Huntington's Disease is known to be an inherited, or genetically-linked, disease, the more that is known about it the more likely a successful treatment, if not cure, will be developed at some point. Since the 1993 discovery of the gene, progress on a treatment or cure has been achieved.
The main advantage to genetic testing for Huntington's Disease, as with other genetic, degenerative disorders, is somewhat limited right now to the basic advantage of knowledge over ignorance. By being tested for this disease, individuals can know whether they have a likelihood to develop the disease over time. According to the National Human Genome Research Institute, "a person who inherits the HD gene, and survives long enough, will sooner or later develop the disease. If the child does not inherit the gene, the child will not get the disease nor pass the gene on to subsequent generations." [www.genome.gov/10001215] By knowing whether or not one possess the HD gene, one can make an informed decision on whether to risk passing the gene onto his or her future children. Also, to the extent a particularly successful treatment for the symptoms of Huntington's Disease is developed, knowledge of whether one carries the gene is vital to the early treatment of those symptoms.
The disadvantage to genetic testing for Huntington's Disease, in contrast to the advantage, is psychological in terms of living with the knowledge of a having a "ticking time bomb" in one's body, and in how medical and life insurance companies respond to that fact about an individual. Historically, knowledge on the part of insurance companies of "preexisting conditions," such as would be the case if one tested positive for the gene for Huntington's Disease, would be grounds for refusal of coverage. Under the federally-passed health care reform law, the Patient Protection and Affordable Care Act, individuals with preexisting conditions are not supposed to be denied coverage for those conditions. The Pre-Existing Condition Insurance Plan that resulted from passage of that Act was intended to address that problem, but implementation of the Plan has run into funding problems, and patients are facing the kind of financial difficulties the new law was intended to prevent. [See "High Bills Faced by Patients With Pre-Existing Conditions Show Obamacare Weakness," Huffington Post, September 9, 2013]
It is up to the individual to decide whether or not to be tested for the gene for Huntington's disease. If the new health care statutes work as intended, then the only disadvantage to testing is psychological; if the law fails for whatever reason, one can add rejection for insurance coverage to that list.