The science and practice of testing for Huntington's disease
Who is at risk for HD?
HD is a hereditary disorder, meaning that it is passed on genetically through generations. Thus, in almost all cases, there must be a family history of HD in order for one to be at risk for developing the disorder. (Exceptional cases may be if family members who had the HD allele died at an early age before symptoms appeared, or if they were misdiagnosed as having another disorder with HD-like symptoms. Also, although very rare, cases of new mutations have been documented).
HD is inherited in an autosomaldominant pattern, meaning that inheriting only one copy of the HD allele from a parent is sufficient to cause an individual to develop HD. Thus, a child who has one affected parent has a 50% risk of inheriting the mutated version of the Huntington gene and eventually developing HD. In reality, this “50% risk” reflects the equal probabilities that either the individual carries the HD allele and will develop HD; or, that the individual has all non-HD alleles and will not develop HD.
Thus, the most common candidate for genetic testing is an adult whose parent has the HD allele or is at risk for having the HD allele. Other cases of genetic testing are discussed in the next section, Part 4. For a more in-depth explanation of the inheritance of HD, click here.
Last Modified: 9-13-02
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