At-risk
meaning the patient has a parent or sibling who has tested positive for the Huntington's disease
(HD) gene.

Anticipation
occurs when a child develops a disease earlier than his or her parent.

CAG Repeat
the repeating unit of DNA ("triplet repeat") present in all normal huntington genges, which when expanded to 36 or more units ("mutant") causes HD.

Chorea
refers to involuntary twitching movements that first tend to involve the fingers and toes and then progress to include the whole body

Dementia
refers to a gradual loss of intellectual abilities such as memory, concentration, problem solving, and judgment.

Genetic testing
when a person gives a blood sample so that he or she can be tested for the presence of a specific hereditary disease.

Hereditary
meaning that it is caused by a gene that is passed from parent to child.

Movement disorder
The movement disorder associated with HD consists of two parts: involuntary twitching movements (chorea) and difficulties with voluntary movements in the form of clumsiness, stiffness, or trouble with walking.

Neurodegenerative
meaning that it is a progressive condition, which results from accumulating damage to specific areas of the nervous system

Psychiatric disturbances
meaning that the patient may develop depression, mania, irritability, apathy or personality changes.

Personality changes
changes in behavior or interactions with other people that so no not fall into another diagnostic category.

Presymptomatic
when someone is carrying the abnormal ("mutant" or "expanded") gene, but does not yet have symptoms of the manifest disease.

Recessive
meaning that one must get the gene from both sides of the family to have the disease.

Symptomatic
meaning that a person is carrying the abnormal gene, and showing signs and symptoms of the disease.