Huntington's disease is an inherited neurodegenerative disorder. It is passed from parent to child in an autosomal dominant manner, meaning you need only one copy of the gene to inherit the disease. This is in contrast to an autosomal recessive disorder which requires two altered genes to inherit the disorder or an altered gene from each parent. If you have the gene and live long enough, you will eventually develop HD and each of your children has a 50% chance of inheriting the gene. If you do not have the HD gene, you can not pass it on to your children and they can not pass it on to their children. There are no "carriers" for HD.

The HD gene is present from birth, but the age of onset is usually in the third or fourth decade of life. While this is the most common time for symptoms to appear, there have been reports of onset as young as 2 and as old as 80. Symptoms begin gradually and progress over time. It is important to remember that no one dies of HD but rather with HD. Because of this, quality care and attention to changes in the affected individual's condition can often prevent or minimize complications and increase quality of life.

Huntington's disease affects three main areas of function: motor, mood, and cognition. Motor disturbances can fall into two categories: too much movement and too little movement. Chorea (involuntary dance-like movements) can affect any part of the body. It is commonly seen as restless, wriggling movements of the fingers or toes in the early stages of the disease. Movements tend to become larger over time and can involve the face, arms, trunk and legs. Chorea may appear more pronounced when an individual is under stress or experiencing an extreme of emotion. It tends to lessen in the later stages of HD. Rigidity or muscle stiffness and slowness may also be present. This is more common when onset occurs in childhood or adolescence and also in more advanced disease. Both chorea and rigidity can interfere with mobility and coordination.

Changes in mood are often first noticed by family members. Depression is quite common and may be present before onset of other symptoms. Anxiety, irritability and temper outbursts, mania and psychosis are other syndromes that can be seen.

Cognition (the mental process characterized by thinking, learning and judging) is affected early in the disease process and worsens over time. Individuals may notice difficulty with memory, calculation, verbal fluency and judgment. It can be especially challenging for the person with HD to attempt to learn a new task.
 
 

Diagnosis of HD relies heavily on a thorough neurological examination and positive family history. Radiological studies such as CT or MRI scans can further substantiate the diagnosis. Laboratory tests may be used to rule out other conditions that can appear similar to HD.

The gene responsible for HD was located on chromosome 4 in 1993. It is the equivalent of a genetic "stutter" meaning that the defect is due to an abnormally long repeated sequence of a certain segment of DNA. With the isolation of the gene, testing for the presence of the gene in unaffected individuals became a possibility. This is called predictive testing and is done by analysis of DNA obtained from a blood sample. It is important to remember that even if you have the gene, the predictive test will not tell you when you will begin to display symptoms. This remains a clinical diagnosis based on an examination by a skilled neurologist.

Certainly not everyone at risk wishes to know their status in regards to the HD gene, and it remains a highly individualized choice. There is no right or wrong decision. Persons interested in taking the test will work extensively with a trained counselor, psychologist or psychiatrist to explore all the implications of the test results. Individuals who are considered to be depressed or unable to accept the potential test result would experience a delay in the testing process until such issues were resolved.

If you decide not to pursue testing yourself, banking or storage of your DNA is strongly encouraged. DNA may be stored indefinitely and is then available to other family members for future use. Your stored sample may be the necessary link in the accurate testing of your offspring. Banking of your DNA is one of the greatest gifts you can leave your children and grandchildren.