Huntington’s Disease – Is It a Genetic Disorder?

Huntington’s disease is a genetic disorder of the brain, and it affects people of all races through out the world. Huntington’s disease is a hereditary disease. It is believed that there is nearly 50% chance of inheriting the disease, by the children of parents who are afflicted with Huntington’s. The disease gets its name from George Huntington, an American physician. He published a paper on what he called “hereditary chorea” in 1872. In the paper published by him he has tried to correctly describe the consequences of this disease on various generations of a family living in Long Island, New York. An interesting fact is that George Huntington’s father, George Lee Huntington, and grandfather, Dr. Abel Huntington, who were both physicians, have also registered their reflections on the same stricken Long Island family. The findings of his father and grandfather had an impact on the young George Huntington’s and these findings played an important role in publishing his paper.

Huntington’s disease is classified as “trinucleotide repeat disorders” which is one of various genetic neurological diseases. Each of the diseases shows many physical, behavioral and cognitive symptoms. But when it comes to Huntington’s, the behavioral and cognitive symptoms differ from patient to patient and are generally not discerned early during the disease’s progression. Physical indications are the same among all patients. Doctors who diagnose the disease usually take these physical symptoms as the first sign. Distinctive physical indications of Huntington diseases are random, unmanageable jerky movements called chorea, which is derived from Greek meaning “circle dance”. The symptoms become worse with the progression of the disease and it results in walking, swallowing and talking troubles. Cognitive and behavioral indications also worsen in the latter stages of the disease. However, Huntington’s disease by itself does not result in death; but cumbersomeness, from the disease such as asphyxiating or infection may cause death.

The attack of physical symptoms of Huntington’s disease can occur at any age, but it should be noted that the disease mostly starts in people in their mid-life, between 30 and 50. Almost nearly 15 or 20 years after the first physical indications show themselves, death will occur. Approximately 10% of Huntington’s start in patients who are below the age of 10. This form of the disease is known as Juvenile Huntington’s Disease.

Research

In 1993, the Huntington’s Disease Collaborative Research Group separated the exact gene which is accountable for the disease. This study resulted in accurately testing the disease only through a blood sample. Before this research, the disease had to be tested by a process of linkage analysis. This testing method involved blood samples taken from various members in a family with a history of Huntington’s. Testing for Huntington’s disease, particularly in minors, have much moral significance. Since a positive test for Huntington’s in an individual will entail their family members as being at risk from the disease. Testing for Huntington’s is mostly not extended to those below 18 years of age.

The exact mechanism of the disease is not yet known. An all-inclusive research is being carried out on the causes and probable remedies of Huntington’s. Intrabody therapy, where genetically engineered intracellular antibody fragments are introduced to fight Huntington’s and various other neurological disorders shows promise. Other techniques utilizing innovative genetic and medical technology such as gene silencing and stem cell implants are also under way. Several new drugs to help combat the symptoms of Huntington’s are also being tested with some like HD-02 and ACR-16 reaching phase-3 clinical trials, which are encouraging signs of the drugs’ efficacy.

Huntington’s Disease

What is Huntington’s Disease?

Huntington’s Disease is a genetic disorder of the central nervous system. Also known as Huntington’s chorea, the disorder is named for the American physician who initially described the condition in 1872. The disease is caused by the inheritance of a faulty gene.

Symptoms classically appear when the person is in their 30’s or 40’s, however symptoms can begin earlier but be less obvious. According to a review article by The University Of Iowa (2003) “The average survival time after diagnosis is about 15 to 20 years, but some patients have lived 30 or 40 years with the disease”. There too are cases where the disease has not manifested itself until much later in life, therefore a good quality of life can be lead until such times as the disease becomes unmanageable.

Physical Symptoms of the Disease

Huntington’s Disease affects a person in both physical and psychological ways. Psychiatric manifestations vary and may precede motor and cognitive changes. “Personality changes and depression occur most commonly. Paranoid schizophrenia-like symptoms occur in 6% to 25% of cases” (Correa et al, 2006).

Motor Disturbance – the signs of this initially present with ‘clumsy’ behaviour. Due to erratic and random movements of the arms and hands the person may not have the same control over their actions as before. Initially these symptoms can be subtle and it is not uncommon for the person to attribute them to other causes. Unfortunately diagnosis can be delayed as the person suffering may often disguise these behaviours due to embarrassment or denial. The way a person walks is often described as ‘dance-like’ and in the early stages it is not uncommon for people to be thought of as if in a drunken state with the inability to remain with a fixed posture. As the disease progresses other symptoms may include:

o Postural instability
o Inability to sustain certain voluntary postural movements
o Poor control of the tongue and diaphragm
o Poorly articulated and slurred speech.
o A strained and sometimes inappropriately loud voice.

Cognitive Decline – Progressive mental impairment, dementia-like behaviour along with lack of comprehension and memory are symptoms which the individual will acquire over many years. Due to an increase in cognitive impairment they are likely to need assistance with communication as recognizable words and conversation become difficult.

Neurobehavioral Changes – Emotional and behavioural changes develop over time. With direct effect on the personality of the individual, they may display signs of:

o Irritability
o The need to criticize
o Complaining
o Suspiciousness/paranoia
o Impulsiveness
o Lack of self-control

Because these irreversible symptoms are difficult to cope with individuals who suffer with the disease often become clinically depressed displaying signs of hostile and manic behaviour.

(We Move, 2008)

Diagnosis of the Disease

Many years ago Huntington’s Disease was a difficult one to diagnose. With advances in research and recognition of symptoms people are more likely to be diagnosed much earlier in the disease process. Because symptoms can involve those similar to people suffering mental illness, for year’s people would be housed in mental institutions without ever gaining a clear diagnosis.

Nowadays access to correct diagnosis and care is far more efficient. A neurologist will gain a full medical history (particularly taking into account any hereditary diseases), complete a physical examination and generally assess the individual’s mental capacity and function. For those displaying obvious symptoms, to an experienced medical eye, a diagnosis may be possible on this assessment alone however diagnostic tools are used in every case.

It was not until 1993 that the discovery of the Huntington’s disease gene was discovered (HDA, Date Unknown). Resulting in a genetic test to search for the presence of the gene. The test is performed using a blood sample and it analyzes DNA for mutation of the disease. Since the mutation in the Huntington’s disease gene has been identified it is fortunate to know that those who will or will not develop the disease can be identified with certainty (Huntington’s Disease Collaborative Research Group, 1993).

The use of CT scans and magnetic resonance imaging can also be useful tools in assessing the physical structure of the brain. These tests do not act as a conclusive diagnostic tool however twinned with genetic sampling and the presence of symptoms they can provide further useful information (MedTv, 2006)

Counseling is always offered prior to undertaking genetic testing. It is essential that the individual concerned is aware of the possible impact a definite diagnosis is likely to have on them. Unlike many other diseases Huntington’s has no known cure; therefore the impact of this on the newly diagnosed individual may be profound.

There are three categories of genetic testing they are performed at the following stages:

1. Prenatal testing – a pregnant woman will have the choice whether they wish to undertake genetic testing of their unborn child. Amniocentesis or chorionic villus sampling give the ability to test for the Huntington’s disease gene before the infant is even born. This test would not be suggested unless there was significant cause to suspect the presence of Huntington’s in the child. The parents would be required to undergo counseling before the test went ahead.

2. Pre-symptomatic testing – for those with a proven family history genetic testing may be desirable as a measure of risk as to whether the gene is being carried. For some people it is important that they know in the event that they themselves develop the disease, for others they prefer not to know and live in hope that they are fortunate enough not to.

3. Confirmatory testing – as previously mentioned this test is used to confirm the suspected diagnosis of Huntington’s disease in individuals whom are already displaying symptoms.

The Hereditary Nature of the Disease

According to Johns Hopkins Medicine (2007) “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”.

Treatment and Management

To date there is no known prevention or cure for Huntington’s disease. Research is however ongoing with the help of willing participants who have the disease, to seek more information in a hope to eventually combat the debilitating disease.

Medications – such as tranquilizers, and anti-psychotic drugs can help control movements, violent outbursts and hallucinations associated with the disease (MFMER, 2007) . In some cases these medication can cause individuals to enter a zombie-like state however when physical safety may be an issue this medication is necessary.

Commonly used are medications to treat symptoms of associated depression. These help to lift mood and enable the individual to cope better emotionally.

Speech therapy – this is used when recognizable speech becomes a problem for the individual. Due to the neurological symptoms they may too have problems with swallowing and a speech and language therapist will assist with both problems. The ability to communicate for those who suffer is paramount therefore they should be supported in doing this wherever possible.

Occupational therapy – this assistance will enable the individual to maintain their independence and ensure for as long as possible they can continue essential activities of daily living. Therapists work closely with those suffering to ensure they make use of their hands and other physical functions to avoid the risk that lack of use will result in the inability to use them at all.

Long-term Care

As the disease progresses the individual will be less able to care for their own personal needs. With gradually worsening dementia and motor dysfunction immobility becomes almost impossible, dietary intake lessens due to loss of appetite and ability to intake regular meals, also the individual is likely to have problems with communication. Long term care is usually considered for those who have a level of symptoms which lead to an ability to care independently.

Although the disease itself is not a direct cause of death, the likelihood of malnutrition, excessive weight loss and immobility will render the individual with the disease more susceptible to problems such as chest infections which in the less able patient can lead to death.

Understanding Huntington’s Disease

Huntington’s disease or Huntington’s chorea is a genetic disorder that causes progressive breakdown of the nerves in the brain affecting muscle coordination and eventually dementia and decline in cognitive function. It is more common in Western Europe and less in Asia and Africa. Huntington’s disease usually occurs between ages 35 to 44, but it can also occur during any age.

HD is an inherited disease, caused by a dominant mutation of the gene called Huntingtin. People are born with this defective gene but the symptoms do not usually appear until they reach middle age. When one of your parents is suffering from Huntington’s disease, there is a 50% chance that you will also have it. If both parents have HD, then all their children will also be affected.

The symptoms of Huntington’s disease vary for each individual. During the early stages, subtle changes will be seen in a person’s personality, physical skills and cognition. The initial symptoms are uncontrolled movements of the feet, face, fingers and trunk. These movements are called chorea, which will become worse when you are feeling anxious. There will also be mild clumsiness and problems with maintaining coordination and balance. These will worsen within three years or even earlier depending on the person. Other psychomotor functions will also be impaired and will become more pronounced as the disease progresses. Abnormal facial expressions, difficulty in chewing, speaking and swallowing, sleep disturbances and seizures are also common symptoms of Huntington’s disease.

Aside from the motor function, Huntington’s disorder also affects the cognitive ability of a person. Executive functions are the ones that are especially affected which include abstract thinking, cognitive flexibility, planning and initiating appropriate actions. Later on, the memory will be affected. There will be short-term and long-term memory loss, as well as deficits in procedural and working memory. Over time, these cognitive disabilities will become worse which leads to dementia or the serious loss of cognitive ability.

There are also neuropsychiatric signs and symptoms of Huntington’s disease. Some of them are anxiety and depression, compulsive behavior, aggression and blunted affect or the reduced display of emotions. People with Huntington’s disease also have difficulties in recognizing certain negative emotions from other people. When HD patients are unable to cope well with their disorder, suicide attempts are very common.

For the early management of Huntington’s chorea, diagnosis should be made as early as possible. In people who have higher chances of inheriting this disease are encouraged to have genetic testing. If this has a positive result, it does not necessarily mean that you will have HD but it should encourage you to be cautious enough to observe if you have the signs and symptoms. If the genetic testing result is negative, then you will not develop Huntington’s disease.

As of today, there is still no cure for Huntington’s disease. The treatment is then focused on alleviating the signs and symptoms that are being manifested. The goal of treatment is to improve the quality of life for the person who is suffering from HD. Because it is a progressive disease with no treatment, support systems are necessary so that coping is possible.