Information - Huntington's Disease (HD)

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Information - Huntington's Disease

Information about Huntington's Disease is contained on this page. By clicking on one of the links below, you will move directly down the page to the section of your choice. There is also information and research in our newsletter archives

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Background
HD and inheritance
Symptoms
"Symptom Watching"
Caring for the person with HD
Presymptomatic testing

Background
Huntington's Disease (HD) is an inherited neurological condition. This means that it is a disease of the brain which affects the nervous system and is passed down through a family line.

HD is not a condition which is evident at birth. In fact, symptoms will not usually appear until a person is between 35 and 45 years of age.

HD is caused by a defective gene. A gene is a basic unit of inheritance. Genes are the means by which a child inherits all his or her characteristics. For example there are genes for height, eye colour and baldness. Genes are transmitted to a child at the time of conception. A person carries this set of genes all his or her life. All our genes are in pairs and we inherit one member of the pair from our mother and the other from our father. Sometimes an alteration can occur in a gene so that the gene does not function normally. If the alteration occurs in one of the HD genes then symptoms of HD will eventually appear.

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HD and inheritance
The altered gene for HD is passed from parent to child without regard for sex. In other words, it can be transmitted from a mother or father affected by HD to either a son or daughter.

If a person inherits the altered gene for HD, eventually symptoms of the condition will begin to appear. For a small group of people these symptoms may be evident before they are 35 and for another small group there may not be signs of the disease until after age 45.

Sometimes people who inherit the altered gene for HD will die before the symptoms of HD appear. They may be involved in an accident or have some other illness such as a heart attack. In such cases doctors or other family members might not know that the HD gene was present.

Any child born to a person who carries the altered gene for HD has a 50 per cent chance of inheriting the altered gene. It follows that the child equally has a 50 per cent chance of not inheriting the altered gene. It does not matter whether or not the parent is displaying symptoms of HD when the child is conceived since the symptoms of HD usually appear after a person has begun, or even completed a family. What matters is whether or not they have the HD gene in their genetic make-up. If a person does not inherit the altered gene for HD then his or her children are not at risk of developing HD.

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Symptoms
There are three groups of symptoms for HD; physical, cognitive and those affecting the personality or emotions. There is no specific order or sequence to the symptoms for HD and the experiences of one person may be quite different from those of another.

Physical Symptoms
In the early stages of HD a person is likely to experience some mild twitching of the fingers and toes, and perhaps the face or limbs. He or she may feel a little less co-ordinated, fumbling or knocking things over. As the disease progresses, walking may become more challenging and, as coordination decreases, people affected by HD may begin to trip and bump into objects or people in their path.

Cognitive Symptoms
The term "cognitive" refers to tasks of the brain concerned with knowing, thinking, planning, judging and remembering. In the early stages of HD there may be little evidence that these functions have been affected, but gradually some subtle changes will be detected.

Short term memory may be reduced, with a person affected by HD forgetting small recent happenings, such as the need to pass on a telephone message, turn off the kettle, or attend an appointment made yesterday. Tasks requiring intense concentration or much planning and judgement may become more difficult. Examples may include arithmetic tasks or planning to keep up with a heavy business schedule. Over time concentration for activities such as reading and demanding conversation may be affected.

While HD does impact upon memory, planning and judgement, it does not affect a person's orientation. In other words, people affected by HD can be expected to know and recognise the people about them as well as know where they are, and what day it is.

Personality or Emotional Symptoms
As with the physical and cognitive changes brought on by HD, changes to personality will begin subtly. In the early stages of HD, a person may be more irritable or moody than previously. Depression is common to about a third of all people affected by the condition. Some persons affected by HD laugh or smile at inappropriate times or may feel like crying for no apparent reason.

Final note concerning symptoms
The expression of HD varies from person to person. While some of the cognitive or emotional symptoms may be quite pronounced for one person, they may be much less so for another. However, for all people HD is progressive.

Perhaps the most common symptom of the condition is chorea; that is dance-like or jerky movement of the arms and legs. These movements begin as twitches and gradually increase over a period of years to larger movements. A small group of people affected by HD does not experience chorea. For this reason the condition previously known as "Huntington's Chorea" is now called "Huntington's Disease".

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"Symptom Watching"
Symptom watching is a natural and understandable response to being at risk to HD but it can also be very stressful. Many of the early symptoms of HD such as fumbling, moodiness or forgetfulness are also experienced by members of the wider population (not at risk to HD), particularly when they are under stress. Those at risk of HD may misinterpret such feelings, behaviour or actions as HD. If this happens they may find themselves entering a confusing cycle with anxiety leading to irritability, fumbling and/or forgetfulness with each of these again being interpreted as symptoms of HD.

If symptom watching and concern about being at risk to HD is interfering with your ability to carry out normal activity it may be wise to seek assistance from a GP or counsellor.

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Caring for the person with HD
One of the questions most asked about HD, once a person shows symptoms of HD, is "How long does it go on?" This is difficult to answer since HD affects people differently. It is usually a slow, but progressive condition. An affected person may live for 15 to 25 years or longer after developing the first symptoms.

People with HD can improve their quality of life by attempting to remain active physically, mentally and socially. Walking, reading and maintaining friendships are some examples. In short the person with HD should attempt to live as fulfilling a life as possible.

At this point there is no cure for HD, but some symptomatic treatments and support services are available to individuals and families affected by HD. Advice concerning medical treatment should be sought from a GP or specialist.

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Presymptomatic Testing
The gene responsible for HD was identified in 1993 making it possible for those people who are at risk to the condition to take a test to determine whether or not they have inherited the gene. Candidates for testing must be a minimum of eighteen years of age, and must want to know their gene status in order to be accepted for testing. Extensive support, information and counselling are available.

The predictive testing program for Queensland is coordinated by the Queensland Clinical Genetics Service in conjunction with the Aspley Community Mental Health Centre. Individuals can be referred to the service by their local doctor or specialist by writing to:

Queensland Clinical Genetics Service
Royal Children's Hospital
Herston Road, Herston, Q. 4029
Telephone: (07)3636 1686
Fax: (07)3636 1987