Huntington's DiseaseIn 1872, George Huntington, an American physician, researched and published a report on a disease that affected several generations of a family in East Hampton, Long Island. Clinical manifestations reflected Huntington's disease (HD) with chorea, psychiatric and cognitive disturbances, and slow progression of deterioration leading to death. Huntington's disease is an autosomal dominant neurodegenerative disorder of hereditary nature. The National Institute of Neurological Disorders and Stroke (2013) identified 15,000 Americans with HD. At least 150,000 Americans have a 50% chance of developing the disease and their loved ones have a chance of developing HD. The prevalence of HD among populations of European origin is between 3 and 7 cases per 100,000 and remains stable between generations. The prevalence of HD is lower in Chinese, Black African and Japanese populations. Roze, Bonnet, Betuing, and Caboche (2010) reported that in 1952, Venezuelan physician Americo Negrette suspected an outbreak of HD in a small town on Lake Maracaibo in Venezuela. The average age of HD is 35 to 50 years; the range is 2 to 85 years. Fifteen percent of cases occur before age 30. Life expectancy after HD diagnosis is approximately 15 to 20 years. Wahlin and Byrne (2012) identified genetic markers through chromosome mapping of the gene carrying the HD trait in 1983. Ten years later, mutation of the HD-causing HTT gene allowed doctors to predict whether asymptomatic individuals had inherited the gene for a future disease. . The diagnosis of HD is based on the presence of clinical manifestations. Family members have mental and physical difficulties caring for people with HD. Daily life is complicated by...... middle of paper ......is associated with the instability of the trinucleotide repeat on the short arm of the 4th chromosome. When 40 or more CAGs repeat, this reflects complete penetrant, all gene carriers exhibit HD disease. A partial penetrant suggests that carriers show no signs of disease. When 36 to 40 CAGs repeat in the htt gene; Complete penetrance of the disease is not successful due to instability of the mutation, and then a complete mutation occurs in the next generation representing HD. Thirty to thirty-five CAG repeats indicate that the carrier will not exhibit the disease. A longer CAG repeat length likely indicates transmission to the next generation. An unstable trinucleotide repeat is predominant in male gene carriers, occasionally leading to HD in children of affected men and women. A mutation may occur for the first time in a family linked to inherent instability.