Huntington’s Disease: Degeneration of the Brain
EEOB 232: Susan Heaphy
Prize: $50 Gift Certificate
Just imagine watching your spouse, a sibling, or a companion lying in a hospital bed unable to control his/her own body from jerking and speech from slurring. You are not sure exactly what is happening to him/her and you wonder when the last breath will be. The doctor walks in with the test results; the decision is final. Your loved one has inherited the gene for Huntington’s Disease.
Huntington’s Disease, or Huntington’s Chorea, is an incurable, neurological disorder that causes a degeneration of the brain’s nerve cells. This slow eating away of the cells results in dementia, a loss of motor functions of the body, and eventually death (AllRefer.com Health). Dementia is what causes the patient to become dependent upon others. It affects a person’s “memory, language, visual processing and orientation, mood or social skills” and other functions such as “problem-solving abilities, monitoring one’s behavior, and following through on tasks” (Chow p215). George Huntington was first to describe the disease in 1872. He studied chorea in families and traced it back to Europe in the 1600’s (Strange 187-200). According to the Huntington’s Disease Society of America, today, “one out of every 10,000 Americans” has Huntington’s Disease (p2).
Huntington’s Disease is very rare, but it is deadly to those who are diagnosed with it and devastating to those watching a loved one suffer from it. Huntington’s Disease, or HD, is not contagious, but is solely genetic. Those who have the gene pass it on down from one generation to the next and the offspring has a 50 percent chance of developing the disease. “Huntington’s Disease affects males and females equally [crossing] all ethnic and racial backgrounds” and it “does not skip generations” (Huntington's Disease Society of America: FAQ's p1). Carriers of the gene will develop the disease at some point in their life. The onset usually occurs “between 35 and 42 years” of age (Strange 188). Those with a later onset have a “slower progression and less severe symptoms” (p188).
Although the average onset of the disease occurs in mid-life, there is also a juvenile form of the disease in which onset may occur as early as 2 years of age (Huntington's Disease Society of America: FAQ's). Signs of Juvenile Huntington’s Disease include onset before the age of 20, tremor, rigidity, dementia, and slight chorea (Ferri et al.). Fortunately, Juvenile HD is very rare; it only accounts for ten percent of cases of Huntington’s Disease. “Patients with juvenile HD usually inherit the gene from their fathers, those with later onset usually inherit the gene from their mothers” (Ferri et al. p2). Horribly, children with this form rarely make it to adulthood (Huntington's Disease Society of America: FAQ's).
Many have wondered what causes this degeneration of the brain and whether or not we can end this progression. Some studies have been completed and some are still in progress to find the cause of brain degeneration. One thing that Huntington’s Disease affects is the caudate nucleus, a deep part of the brain that is an “important way station” that controls emotions, motor functions, and cognitive functions (Chow p218). Another contribution to the symptoms of Huntington’s Disease is the abundance of the protein “p53” (Molecular Trigger for Huntington's Disease Found p1). The protein with the code for HD activates this “regulatory protein…p53,” which regulates “various mitochondrial genes”and leads to damage in the mitochondria (Molecular Trigger for Huntington's Disease Found p1). This damage to the cells’ mitochondria or “power plants” results in a killing spree of brain cells and loss of brain function (Molecular Trigger for Huntington's Disease Found p1). To follow up progression of this damage, brain scans have been taken and prove that there is a “shrinkage” of the brain in 20 percent of the patients (Strange 189). With as many studies that have been completed and those that are still in progress, there has not been enough information discovered to stop the progression or to find the reasoning for this neuronal damage.
A person may live a normal, every-day life before acquiring the characteristics of Huntington’s Disease. With onset usually occurring mid-life, it is not uncommon for one to live his/her life and have children not knowing that they have the gene for HD. Early signs of the disorder include loss of short-term memory, intellectual decline and dementia (Strange 187-200). Other symptoms include changes in emotion such as depression and anxiety, involuntary movements especially when walking and eye disorders (Strange 187-200). Those with HD may experience problems socially in the work environment and with others (Huntington's Disease Society of America: FAQ's). He/she is often accused of being intoxicated due to the inability to control common behaviors such as walking and standing (Huntington's Disease Society of America: FAQ's).
Later signs include bowel problems, loss of weight, facial twitching, apathy and withdrawal, muscle stiffness or tremor, chorea, mania, delusions, apprehension, impulsiveness, and hostility (Strange 187-200). Voluntary movement is also slowed down and dementia increases as an effect of brain degeneration (Strange 187-200). Symptoms are usually gradual and they are different for each person, related or not (Huntington's Disease Society of America: FAQ's). For example, even if your father's onset of the disease occurred when he was 40, yours may not occur until you are 60. Some may develop cognitive problems first and others may have a decline in motor skills first. “Eventually, every person affected by HD requires full-time care” (Huntington's Disease Society of America: FAQ's p1).
No matter the age of onset, the extension of the symptoms, or how much a person with Huntington’s Disease is loved by the family, the symptoms will eventually cause death. Death of patients usually occurs in the “fifth decade of life” (Ferri et al. p2). The actual cause of death is not from Huntington’s Disease itself, but is usually a result from choking, pneumonia, or other infections (Huntington's Disease Society of America: FAQ's). These factors are what cause death in HD patients 85 percent of the time. Suicide is also common for those with HD because of the depression and mental decline that progresses with time. Those with a loved one who has been diagnosed with HD are encouraged to keep an eye out for signs of suicidal behavior (Ferri et al.).
The Huntington’s Disease Society of America claims that “more than a quarter of a million Americans have HD or are ‘at risk’ of inheriting the disease” (p1). In 1993, the HD gene was detected and genetic testing is now available. However, the test can only tell if you have the gene, not when the onset will occur or how strong the symptoms will be (Huntington's Disease Society of America: FAQ's). Recent studies show that those with HD inherited a “faulty gene on chromosome #4” (AllRefer.com Health). Patients tend to have an expansion of a CAG nucleotide in the gene that codes for the protein Huntington. The greater the number of triplet repeats a person has, the more likely symptoms will develop at an early age. With each generation, the onset of the disease may come earlier and the symptoms may be more severe due to a greater chance of increase in the number of CAG nucleotide repeats (AllRefer.com Health). Diagnosis of HD depends mostly on family history and the signs of symptoms in the patient. If the genetic history is unknown, a “caudate atrophy CT head scan” is helpful in finding the gene that codes for HD (Ferri et al. p5).
At this time, there is no cure for Huntington’s Disease. Prescriptions are simply used to control the symptoms associated with this disease. Clonazepam, haoperidol, reserpine, and valproic acid can be used for treatment of chorea. Antidepressants, neuroleptics, and antipsychotics may help treat dementia and changes in behavior (Ferri et al.). Botulinum toxin can be used on patients with continuous muscle stiffness or cramps (Chow p215-224). Unfortunately, reversal of the disease is impossible and there is no way to stop the progression. Therefore, a number of therapies are encouraged including speech, physical, and occupational therapies to help patients become less dependent upon others (Ferri et al.). Those at risk of HD usually choose not to go through with the genetic testing in fear of having the disease and knowing the consequences (Huntington's Disease Society of America: FAQ's). The only way to prevent Huntington’s Disease is to not have children. “Adoption [and] other forms of assisted reproduction” are also encouraged (AllRefer.com Health p3).
It is extremely difficult for families to watch a loved one suffer from this illness and even more difficult knowing that other members of the family may suffer from it as well. Genetic counseling is encouraged for those in this situation, especially if the disease is a hereditary issue (Ferri et al.). Loved ones can also join support groups such as the Huntington’s Disease Society of America. Other than that, support for each other and good care is really the best way to handle the disease in patients. It may not stop progression, but some believe it may help the patient live a happier, healthier life.
Alone, the discovery of the disease was a big accomplishment, but much research is still needed to cure this disease. Studies are being done on fruit flies and mice to see the effects of decreasing the amount of the protein “p53” (Molecular Trigger for Huntington's Disease Found p1). In fruit flies injected with HD, decreasing the p53 protein results in damage to the neurons of the eyes and in mice, it corrects abnormal behavior including a “startled response to loud noise,” which is also found in humans with the HD gene (Molecular Trigger for Huntington's Disease Found p1). The result decreasing this protein in humans is still under investigation and is not yet known. In August of 2005, Yerkes National Primate Research Center of Emory University was granted money for a four-year study of the “transgenic nonhuman primate model of Huntington’s Disease” (p1). They believe this study will give a “better understanding” for not only HD, but for all brain degeneration diseases including Parkinson’s and Alzheimer’s Disease (McNicoll p1). Hopefully this study will result in “better treatment options” and maybe even a cure (p1). However, this research may not be complete for another four years and it may even take longer than that. With as much as we know about Huntington’s Disease, there is still an extensive amount of information yet to discover.
As you can see, the importance of research cannot be stressed enough. Imagine watching someone you know suffer through a disease like this. How horrible it is for someone who lives an active, independent life, someone so intelligent, so caring, and so full of life to go through something like this. Just imagine watching a loved one decline and die from a disease that is incurable. Wouldn’t you do anything in your power to find a cure? I know I would.
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