Huntington's Disease

Genetic Testing: direct mutation analysis

HD is usually inherited as an autosomal dominant trait, meaning that each child of an affected parent has a 50% risk of inheriting the mutated gene for the disease. Those who do not inherit a copy of the disease gene (or have a spontaneous mutation in that gene) do not develop HD and cannot pass the disease trait on to future generations.

The discovery of the IT15 gene in 1993 facilitated the development of specialized testing that may help to confirm the diagnosis of HD in patients with an affected parent or characteristic symptoms of the disease. During such testing, blood samples are taken from patients and DNA is directly analyzed for HD mutations. The DNA is studied through a series of tests known as Polymerase chain reactions or PCR testing. During this testing, the number of CAG repeats within the IT15 gene region is estimated. Additional blood samples may be obtained from close or first-degree relatives (e.g., mother or father) with HD to help confirm the results.