Huntington\'s Disease and Laboratory Investigation

¶ … Huntington's disease and laboratory investigation of this disease. Huntington's disease can attack just about anyone, but it is involved in the genetics of a family. Today, Huntington's disease is treatable, but it is still a devastating disease that has no cure, but researchers are working on long-term treatment for the disease.

Huntington's disease (HD) appears in families, and it can be devastating. One writer notes, "HD is a progressive degenerative genetic disorder, and 50% of the children of a parent with HD will develop the disease (Mendelian autosomal dominant inheritance) and inevitably will become demented" (Ogden 2005, 18). It is a progressive disease that leaves people uncontrolled and unable to care for themselves. A Web site states, "Huntington's disease (HD) results from genetically programmed degeneration of brain cells, called neurons, in certain areas of the brain. This degeneration causes uncontrolled movements, loss of intellectual faculties, and emotional disturbance" (Editors 2010). There is no way to stop the disease or to stop the degeneration that occurs. A doctor first discovered the disease, and untimely the disease was named after him. Author Ogden continues, "In 1872, George Huntington, a North American general practitioner, published the first unambiguous description of this unrelenting neurodegenerative disorder in the Medical and Surgical Reporter" (Ogden 2005, 276). It usually occurs in adulthood, and if a child carries the genetic profile, but does not develop the disease, they will not pass it on to their offspring.

It is not gender specific, it occurs at about the same frequency in men and women. Author Ogden notes, "Death in the more common midlife onset cases usually occurs around 50-60 years of age, so survival length after onset is about 13-17 years. In about 20% of cases, the onset of HD is after 50 years and can happen as late as 84 years of age" (Ogden 2005, 278). Research continues into how the disease develops and why some people who carry the gene do not develop the disease.

There are drugs that help treat the disease and its symptoms, especially the involuntary movements that occur with it. Another writer notes, "In August, the U.S. Food and Drug Administration (FDA) approved Xenazine (tetrabenazine), for the treatment of chorea, the jerky, involuntary movement that occurs in people with Huntington's disease" (Samalonis 2008). However, there is no cure for the disease, and the drugs generally treat the symptoms, but have side effects, such as fatigue and restlessness (Editors). Research into the disease continues, and researchers hope to make a breakthrough in how to control or cure the disease. While the disease is not so prevalent in society, there are small communities that show a propensity for the disease. Researchers studied a small village in Venezuela where a large majority of the population suffers from the disease, due to close genetic ties. The study helped researchers learn more about the HD gene and how it mutates (Ogden 2005, 277). In addition, it seems prevalent in some countries and not in others. It is relatively rare in Japan, but more common in areas of Great Britain, such as south Wales and northeast Scotland (Ogden 2005, 281). Another writer notes, "The disease is relatively rare; approximately 30,000 Americans are symptomatic and another 200,000 are at risk" (Lechich et al. 2008). Laboratory studies into why this is the case are still underway.

Symptoms of the disease usually develop in adulthood. The editors of a Web site on the disease continue, "Some early symptoms of HD are mood swings, depression, irritability or trouble driving, learning new things, remembering a fact, or making a decision. As the disease progresses, concentration on intellectual tasks becomes increasingly difficult and the patient may have difficulty feeding himself or herself and swallowing" (Editors 2010). There are also many motor functions that become compromised as the disease progresses. There are also psychiatric symptoms that occur throughout the progression of the disease. Author Ogden continues, "Dysphoria, agitation, irritability, apathy, anxiety, disinhibition, and euphoria (in order of decreasing frequency) were experienced by 30%-69% of HD patients" (Ogden 2005, 283). The symptoms progressively worsen as the disease progresses, and treatment can only attack the symptoms. It occurs in about 1 of 10,000 cases of the mutated gene that causes the disease.

Laboratory work is extremely important in the research into HD, and it played a major role in finding the genes that lead to the disease. Author Ogden notes, "Before the availability of a specific molecular genetics predictive test for HD, neuropathology was the accepted gold standard for its firm diagnosis" (Ogden 2005, 280). Researchers are also working with laboratory animals to learn more about the disease. The editors note, "Laboratory animals are being bred in the hope of duplicating the clinical features of HD so that researchers can learn more about the symptoms and progression of HD" (Editors 2010). This is important so that researchers can learn what works to treat the disease, and what does not work. In addition, "Investigators are implanting fetal tissue in rodents and nonhuman primates with the hope of understanding, restoring, or replacing functions typically lost by neuronal degeneration in individuals with HD" (Editors 2010). HD is similar to Alzheimer's disease in that both diseases attack the brain and memory, but HD is even more debilitating because it attacks the area of the brain that controls movement and function, so patients lose many of their motor skills, too. Often, family members withstand the worst of the disease, because patients are unable to function on their own. Often, they are committed to psychiatric facilities because they are no longer able to care for themselves or comprehend the world around them.

Usually, tests are used to determine if the patient has the gene that causes the disease, but there is much testing going on to help understand and treat the disease. The editors continue, "Related areas of investigation include excitotoxicity (over-stimulation of cells by natural chemicals found in the brain), defective energy metabolism (a defect in the mitochondria), oxidative stress (normal metabolic activity in the brain that produces toxic compounds called free radicals), tropic factors (natural chemical substances found in the human body that may protect against cell death)" (Editors 2010). All of these tests and research will help doctors fully understand the disease, and that can eventually lead to eradication of the disease.

Genetic testing helps identify the disease, and that has become extremely important in identifying patients with the disease. Ogden continues, "With the isolation of the Huntington's gene and mutation, and the development of an accurate molecular genetic predictive test, genetic counseling has become extremely important" (Ogden 2005, 285). Patients want to know if their children carry the disease, if they carry it, and what their chances of developing it are, so laboratory testing is extremely important long before the disease develops.

There are several new and encouraging developments in testing and treatment for the disease. Although it is relatively rare, families with a history of the disease are becoming more aware of it, and having family members tested to identify who carries the gene for the disease. Author Ogden states, "On occasion parents want to have their young children tested for the gene, but many genetic laboratories decline to do this, as it would remove the ability of the child to decide for himself, when older, whether or not he wishes to know his status" (Ogden 2005, 286). This is understandable, and it poses a quandary for laboratories testing for the disease. Many patients who find out they have the disease suffer depression and other emotional issues, and many spend their lives in dread of the disease developing. There are certainly pros to knowing that you could develop the disease, but it has many cons, as well, and families have to realize that before they request the test. As for the laboratories, they must weigh the advantages and disadvantages of disclosing the genes that cause the disease, and create their own procedures accordingly.

Laboratory testing has also developed new ways to conquer the disease before it starts. Ogden notes, "A recent development in preventing the birth of babies with the HD gene mutation is to inject a number of the father's sperm into a number of the mother's eggs in a laboratory and to test each resulting embryo immediately" (Ogden 2005, 286). Testing the embryo indicates whether the baby will develop the disease, and allows the parents to choose to abort the fetus if it shows signs of the disease. Many parents are choosing this option to ensure their children will not have to suffer from the many symptoms of this terminal disease.

Another breakthrough in the lab is the development of transgenic mice that have allowed researchers learn more about the disease and medications that can help the symptoms. Another writer notes, "The transgenic mice have served to study medications that may be able to protect the brain, might delay the onset of the disease, and slow its progression'" (Goolkasian 2001, 34). This is excellent news for anyone who knows they carry the gene that causes the disease, and for anyone who has watched someone suffer from the disease. HD is extremely debilitating, and if the patient lives long enough, the symptoms can become extremely severe. It is not uncommon for patients who suffer from the disease to suffer extreme depression and sometimes suicide, so developing medications that could delay or slow the disease are extremely important, and laboratory testing should definitely continue in this area.