Huntington's Disease (HD) is a hereditary brain disorder that affects people of all races all over the world. It takes its name from Dr. George Huntington, a Long Island physician who published a description of what he called "hereditary chorea" in 1872. From the Greek word for "dance"= chorein. Chorea refers to the involuntary movements which are among the common symptoms of HD. Therefore Huntington's Disease was at first called Huntington's Chorea. But, because "Chorea" is only one symptom of the three which are characteristic for this desease, it was in later years called Huntington's Disease.
Until quite recently, little was known or published about HD. Yet in the last twenty years, much has been learned about the causes and effects of HD and about treatment, therapies and techniques for managing the symptoms of the disease. In 1993, after a ten-year search, scientists found the gene that causes HD, and important advances have flowed from this dramatic discovery. Many scientists are actively engaged in the search for effective treatments to stop or reverse the effects of HD, and eventually to cure it altogether.
HD is a degenerative disease whose symptoms are caused by the loss of cells in a part of the brain called the basal ganglia. This damage to cells affects cognitive ability (thinking, judgment, memory), movement, and emotional control. Symptoms appear gradually, usually in midlife, between the ages of 30 and 50. However, the disease can strike young children (juvenile form) and the elderly.
In most cases, people can
maintain their independence for several years after the first symptoms of HD
appear. A knowledgeable physician can prescribe treatment to minimize the impact
of the symptoms. Allied health professionals, such as social workers, occupational
and physical therapist, speech-language pathologists (speech therapists) and
nutritionists, can all play a useful role in maximizing abilities and prolonging
HD occurs in approximately 1 in 10.000 people in most "western" countries. In other countries the prevelance may be much lower.
Males and females have an equal chance of inheriting the gene from an affected parent.
Those who do not inherit
the mutated gene will not develop the disease, nor will their children; HD does
not "skip a generation". Genetic testing is available
to determine whether or not a person carries the mutated gene for HD.
Children and adolescents must face living with a mother or father who is ill and whose behaviour may be erratic. They may even be asked to participate in the parent's care. For parents, telling children about HD can pose difficult questions. Should a child/children be told about HD? If so, at what age. When is a child old enough to cope with the idea of being at risk for HD?
There are no easy answers,
particularly since children develop at different rates and each family situation
is different. Generally, it is a good idea to be as open as possible without
being alarmist, and to convey the facts bit by bit. This way, a child can develop
a gradual awareness of HD rather than being suddenly overwhelmed by information.
Physical symptoms may initially
consist of "nervous" activity, fidgeting, twitching, or excessive restlessness.
Handwriting may change and facial grimaces may appear. Day-to-day skills involving
coordination and concentration, such as driving, become more difficult.
These initial symptoms will gradually develop into more marked involuntary movements of the head, trunk and limbs - which often lead to problems with walking and balance.
Speech and swallowing can
become impaired. Movements generally tend to increase during voluntary effort,
stress or excitement and decrease during restand sleep.
Early in the disease, manifestations include subtle changes in coordination, perhaps some involuntary movements, diffcult thinking through problems, and often, a depressed or irritable mood. At this stage, medications are often effective in treating depression and other emotional symptoms. It is a good time to begin planning for the future. Financial plans should be made and legal documants drawn up.
In the middle stage, involuntary movements (chorea) may become more pronounced. A staggering gait can sometimes be mistaken for drunkenness. Speech and swallowing will begin to be affected. It is important to consult a speech therapist who will be able to offer suggestions and strategies for improving communication and swallowing abilities. Likewise, occupational and physical therapists can develop programs to help maintain the highest level of functioning and thereby improve quality of life.
Thinking and reasoning skills will also gradually diminish. At this stage it may become increasingly difficult to hold a job and to carry out household responsibilities. Here again, simple strategies may be employed to help decrease frustration, increase funtioning and prolong independence. For example, disorientation and short-term memory loss can be addressed by labeling drawers, maintaining a daily routine ans posting a calendar appointments and events.
People with late stage HD may have severe chorea, but more often have become rigid. Choking on food becomes a major concern, as does weight loss. At this stage people with HD are totally dependent on others for all aspects of care, can no longer walk, and not able to speak.
Although cognitive abilities are severely impaired, it is important to remember that the person is generally still aware of his/her environment, remains able to comprehend language, and remains an awareness of loved ones and others. He/she may continue to enjoy looking at photographs and hearing stories of family and friends.
People do not die from HD
itself but rather from a complication of the disease, such as choking or infection.
Death generally occurs about 15 to 20 years after onset.
MRI (Magnetic Resonance Imaging) or CT (Computerized Tomography) scans may be included in the exam but the findings from these procedures are not sufficient to form a diagnosis.
Similarly, a genetic test may be used to help confirm, or rule out, a diagnosis of HD. However, a positive test result (indicating the presence of the HD gene) is not sufficient in and of itself to confirm a diagnosis of HD.
It is best to see a neurologist who is very familiar with HD, as the symptoms can mimic those of other disorders such as Parkinson's Disease or alcoholism. Referrals to knowledgeable professionals can be provided by your local or national HD organisation.
For some, a diagnosis of HD can be a relief. It may provide an explanation for why their memory is not quite as sharp as it used to be or why they are feeling irritable or depressed. Others find the news very upsetting.
It is not uncommon for people
to be in a state of "denial" when they are first diagnosed with HD. Regardless
of their initial reaction, it can help to discuss the situation with others,
either in a support group, with a social worker or with a counselor or therapist.
Initial symptoms usually
involve slow, stiff and awkward walking and talking, choking, clumsiness and
falling. Later, the child may become slow to respond and performance at school
may become erratic. The course of the juvenile form is generally more rapid
than the adult-onset HD.
Being at risk for HD influences major life choices such as marriage, family planning and carreer decisions. It can also have a pervasive influence on every day activities. An episode of clumsiness, twitching or forgetfulness, such as everyone experiences from time to time, may be seen as a potential symptom of HD and can take on nerve-racking significance.
Many people come to accept the uncertainty of being at risk for HD, especially in the absence of an effective treatment or cure for the disease. Indeed, faced with the choice, most prefer to live with this uncertainty rather than taking a pre-symptomatic test, which could remove hope by confirming that they will develop HD.
For others, genetic testing
for HD offers a chance to end the uncertainty and to gain information which
they believe will enable them to make informed choices about the future.
The HD gene was found to contain a specific section that was expanded in people with HD. In all people, this stretch of genetic material, or DNA, contains a pattern of so-called "trinucleotide repeats". Nucleotides are the building blocks of DNA and are represented by the letters C,A,G and T ( Cytosine, Adenine, Guanide and Thymine). In most people, the repeated pattern "CAG" occurs 30 times or less. In HD, it occurs more than 36 times. There are people with a CAG repeat in the so called "grey zone", between 30 and 36 repeats. If the person is a male, than it could be possible that his child(ren) has/have more than 36 repeats and will develop the disease. At the moment is not sure that somebody "high in the grey zone" may get the disease at a late age (above 60 or later) or not.
By analyzing a person's DNA and counting the number of CAG's, it is possible to tell if that person will develop HD. The test cannot predict the age of onset, but the juvenile form has normally more than 50 repeats upto more than 120.
The decision to undergo genetic testing is an intensely personal one and one that cannot be taken lightly. Everyone has their own circumstances to take into consideration, and there are no "right" or "wrong" answers. Testing should never be forced upon an at-risk individual. Children are generally not able to consider the full implications of testing and may be vulnerable to pressure from others. Therefore, the minimum age requirement is usually 18.
Various resources are or should be available to asssist you in making this decision. HD societies, social workers, genetic counselors at testing centers can help. Testing should only be done at (academic) testing centers where teams of professionals who are knowledgeable about HD are available.
The testing procedure involves sessions with various professionals. It typically includes one session devoted to each of the following: genetic counseling, a neurologic exam, a psychological interview, discussion of the results and follow-up. The genetic test itself is a blood test.
The purpose of the preliminary sessions is to ensure that the person understands the potential implications of his/her genetic status and is prepared to receive the results. The neurologic exam will determine if any early symptoms of HD are present. If the person is found to be symptomatic, he/she will be offered the option of discontinuing the testing procedure.
It is important to note that presymptomatic testing for HD cannot dertermine when the disease will begin or its course or severity. People who test positive for the gene may remain healthy for many years. HD can only be diagnosed by a neurological exam.
Recognizing that medical,
ethical, legal and social issues arise from the availibility of predictive testing,
recommendations concerning the use of a predictive test for the detection of
HD were drawn up by a committee consisting of representatives of the International
Huntington Asociation and the Research Group on Huntington's Disease of the
Worlf Federation of Neurology. These Guidelines, are approved and published
in Neurology 1994; 44: 1533-1536 and J. Medical Genetics 1994; 31: 555-559
Some doctors may prescribe drug treatment when it is not absolutely necessary. In many cases, people with HD do better when medication is kept to a minimum. Often, drugs that are effective at one stage of the disease may not be effective at another.
For these reasons, it is preferable to locate a neurologist with expertise in HD. Not all neurologists are familiar with the disease. Though a family physician is not likely to have much experience with HD, that physician should remain involved in ongoing care and treatment. The person with HD and family members play a critical role in monitoring and assessing the effectiveness of any care and treatment.
It is also helpful to consult a physician or occupational therapist and a speech therapist so that strategies that can have a positive and lasting impact on the quality of life can be implemented early.
Nutrition is important in everyone's life, but takes on added significance in HD. People with HD require an unusually high number of calories to maintain their body weight.
Maintaining, or even gaining, weight can help reduce involuntary movements and other symptoms, particularly in the later stages of HD. Nutritional supplements can help and a nutritionist can offer other valuable suggestions.
Often the best advice and emotional support one gets is from someone who "has been there".
The mutual support given
and the knowledge shared are the reasons that many find HD
support groups to be an important part of their lives. Support groups
are located in many countries.
After the gene discovery, an international coalition of scientists, known as the Huntington Study Group (HSG), was formed to conduct basic and clinical research facilities with teams of doctors with expertise in treating HD. The group has begun to test new drugs which could potentially lead to effective treatment for HD.
For couples planning a family, prenatal testing of a fetus is also an option. A "nondisclosing" variation of the prenatal test can also be done using linkage analysis (also called "exclusion test"). Instead of examining the gene, this method of testing compares patterns of chromosomal inheritance in several family members with the chromosomes inherited by the fetus. In this way, the approximate risk that the fetus is carrying the HD gene can be determined without disclosing the genetic status of the at-risk parent.