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A Brief History
of Huntington's Disease (HD)
Huntington's disease (HD) is named after George Huntington, who
described it among residents of East Hampton, Long Island in 1872.
It is a hereditary neurodegenerative disease. In 1993, a collaborative
group of investigators discovered the gene that causes HD. As a
result of this discovery it is now possible to diagnosis HD via
blood or tissue samples, thus ensuring proper diagnosis of this
disease.
The Genetic
Cause of HD
HD is caused by mutation in a gene located on chromosome 4. This
gene is found in every human being, and contains a triplet repeat
sequence. We have not yet discovered the gene's normal function.
In a case of Huntington's disease, the gene contains an abnormally
large number of triplet repeats. The larger the number of triplet
repeats, generally speaking, the earlier in life one will develop
Huntington's disease. Furthermore, when the gene is passed from
father to child, but not when passed from mother to child, the gene
may lengthen even more, resulting in an earlier age of onset for
the disease. This phenomenon is known as anticipation.
Genes for diseases can be either dominant or recessive. The gene
for Huntington's disease is dominant. Therefore, most HD sufferers
have one copy of the expanded gene and one copy of the normal gene.
Each child of an affected parent has a 50/50 chance of getting an
expanded copy of the gene, and therefore has a 50% chance of inheriting
the disease. On the other hand, if a person with a parent suffering
from HD does not inherit the mutant gene, they cannot pass it on
to anyone else.
Important Information
About HD Testing
It is important to understand that while people are born with the
mutated gene for Huntington's disease, in most cases they will not
develop the symptoms until later in life. Therefore someone can
be presymptomatic for a number of years. In the past, there was
no way to test for the expanded gene, but now a blood test can determine
whether or not an individual carries the gene for Huntington's disease.
This test can be used in cases of suspected HD, to confirm the diagnosis,
or it can be used as a predictive test in individuals who are at
risk as a predictive test. A person who is at risk may want to undergo
predictive testing in order to put their mind at ease, to plan for
their medical needs, or prior to having children. The decision to
have such a test is a momentous one and should not be taken lightly.
Most centers that do predictive testing, including ours, require
a period of counseling before and after the test.
What
Are the Characteristics of HD?
Onset is usually in mid life, but can occur any time from childhood
to old age. Initial signs of this disorder may be subtle. HD is
characterized by a movement disorder, dementia, and psychiatric
disturbances. Additional characteristics of HD include personality
changes, as well as weight loss (probably from a combination of
difficulty eating, and calories burned by the involuntary movements),
difficulty swallowing, and hard to understand speech.
The Course of
HD
Once an individual becomes symptomatic for Huntington's disease
the course of the disease can last anywhere from ten to thirty years.
Typically, the course of HD can be roughly divided into three stages.
| Early Stage: |
In this stage patients can still perform most
of their usual activities. They may still be working and may
still be able to drive. Involuntary movements are mild and infrequent,
speech is still clear, and dementia, if present at all, is mild.
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| Middle Stage:
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At this stage patients are more disabled and need
may assistance with some of their activities of daily living.
Falls, weight loss, and swallowing difficulties may become a
problem. Dementia is more obvious to the casual observer. Involuntary
movements are more pronounced. |
| Late Stage: |
Patients entering this stage of the disease require
almost total care and may reside in hospitals or nursing homes,
although others remain at home. They may no longer be able to
walk or speak. A person may be more rigid now and show less
involuntary movements. Individuals in this stage may or may
not be able to swallow food. At this stage most patients do
not seem to suffer much as they are apparently unaware of their
surroundings. When the patient passes away the cause of death
is usually related to the same natural causes that lead to death
in other severely debilitated patients, such as malnutrition,
pneumonia, or heart failure. |
What Treatments
Are Available?
At this time, there is no cure for Huntington's disease. Researchers
are working on a number of treatments, which may slow down the progression
of the disease. There are a number of interventions available today
that improve the quality of life for HD sufferers. In the early
and middle stages of the disease, medications can be given in small
doses to HD patients to help suppress the involuntary movements.
Depression and other psychiatric conditions in people with HD can
be quite effectively treated. Proper nutrition, exercise and precautions
in the home can help minimize many of the potential consequences
of HD such as weight loss, falls, and choking on food. Finally contact
with other HD sufferers, family members, and care-providers can
be a vital source of support for HD patients, their families, and
loved-ones.
Future Care
People with Huntington's disease should discuss their concerns and
wishes about treatments/interventions (feeding tubes, resuscitation
requests) and autopsies with their families and doctors while they
are still able to speak for themselves.
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