The Huntington disease is a genetic brain disorder initiated by mutations in the HTT gene in the DNA that is then inherited by subsequent offspring(s) as an autosomal dominant disorder (Koff, 2012).
Symptoms of the disorder
Most of the symptoms of this disease are vivid at adulthood, occurring mostly when an individual is between the age of 30 and 40. A rare type of this disease, the juvenile form, however, manifests itself in childhood and adolescent stage. The signs and symptoms of this disease are both physical and behavioral. These types of symptoms may occur in any sequence, but the physical ones are the more easily noticeable of the two (Koff, 2012). Physical symptoms associated with Huntington’s disease include chorea, in the form of small involuntary and uncompleted movements which later develop to twitching and uncontrolled jerking. This causes problems during walking, swallowing and speaking. Other physical signs include general restlessness, abnormal facial expressions, inability to coordinate muscular activities and sleep problems. Cognitive and behavioral symptoms associated with the disorder include impairment in planning, unreasonable thinking, reduced comprehension and lack of flexibility. Ability to judge between appropriate and inappropriate actions is also affected. Memory sequences affected include episodic, procedural and working memory with psychological signs such as depression and aggression being evident.
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It is worth noting that the existence of egocentrism and compulsive behavior in affected individuals can initiate and worsen an individual’s addictions to such behaviors as drug use, and gambling. These psychiatric problems have contributed to suicidal attempts among this group of people which often makes the immediate caregivers consider institutionalizing the affected person. Individuals with this disorder usually live for 15 to 20 years after the onset of the symptoms and eventually die.
How it is inherited
An HTT gene that exists in every individual’s DNA segment, called CAG trinucleotide repeat, is responsible for the manufacture of the huntingtin protein. This protein plays a yet-to-be-defined role in the nerve cells in the brain. It is the mutations in this gene that cause the Huntington disease. This segment should normally be repeated 10 to 35 times within the DNA complex. In some cases, however, a mutation occurs creating more than 40 repeats of the gene in the DNA, which leads to the development of the symptoms associated with the disorder (Koff, 2012). This increase in the number of the repeats of the CAG trinucleotide causes the production of unusually long huntingtin proteins which later fragment into smaller toxic parts and build up in the nerve cells affecting their normal functioning. The disorder is then inherited when a parent whose DNA composition has mutated passes it on to the offspring. The probability that the altered gene will be passed to the offspring is usually 50% depending on the dominance of that parent’s genes in relation to the other parent. The CAG trinucleotide increases as the altered gene are passed to subsequent generations. The increase causes an earlier onset of the symptoms, called anticipation. When the symptoms are evident during childhood, the DNA structure has more than 60 repeats of the gene (Koff, 2012).
Number of people with the disorder
It is estimated that one person in every ten thousand people has Huntington’s disease. This translates to about 30,000 people in the United States alone. Its prevalence is not limited to geographical positioning, race or sex (Milunsky, 2010).
Significance of the Huntington’s disease
The presence, or absence thereof, of this genetic disorder, has wide implications for the societal setting on the individual exhibiting the initial signs of the disease. The main issue is how to measure cognitive maturity in deciding how eligible a person is to take the genetic test used to evaluate the presence or absence of the disease. When drawing insurance and employment plans, this information is necessary for evaluating risk which raises issues of the patient’s right to confidentiality. Another controversial issue surrounding the disease is the prenatal genetic testing that seeks to avoid an incidence of a child being born with certain hereditary diseases (Milunsky, 2010). This would result in selective abortions which have a wide range of ethical repercussions. The treatment procedures of these cases are also of interest to international organizations like the Hereditary Disease Foundation and the CHDI Foundation in the United States. The occurrence and development of the signs of Huntington’s disease also have an effect on the life of the affected person, in particular, his or her immediate caregivers and ultimately the larger society.
References
Koff, R. B. (2012). Huntington disease: 10-year Analysis .
Milunsky, A. (2010). The prenatal diagnosis of hereditary disorders (4th ed., Vol. 2). Springfield, IL: Thomas.
