<Tr> <Th> Frequency </Th> <Td> 4--15 in 100,000 (European descent) </Td> </Tr> <P> Huntington's disease (HD), also known as Huntington's chorea, is an inherited disorder that results in death of brain cells . The earliest symptoms are often subtle problems with mood or mental abilities . A general lack of coordination and an unsteady gait often follow . As the disease advances, uncoordinated, jerky body movements become more apparent . Physical abilities gradually worsen until coordinated movement becomes difficult and the person is unable to talk . Mental abilities generally decline into dementia . The specific symptoms vary somewhat between people . Symptoms usually begin between 30 and 50 years of age, but can start at any age . The disease may develop earlier in life in each successive generation . About eight percent of cases start before the age of 20 years and typically present with symptoms more similar to Parkinson's disease . People with HD often underestimate the degree of their problems . </P> <P> HD is typically inherited from a person's parents, although up to 10% of cases are due to a new mutation . The disease is caused by an autosomal dominant mutation in either of an individual's two copies of a gene called Huntingtin . This means a child of an affected person typically has a 50% chance of inheriting the disease . The Huntingtin gene provides the genetic information for a protein that is also called "huntingtin". Expansion of CAG (cytosine - adenine - guanine) triplet repeats in the gene coding for the Huntingtin protein results in an abnormal protein, which gradually damages cells in the brain, through mechanisms that are not fully understood . Diagnosis is by genetic testing, which can be carried out at any time, regardless of whether or not symptoms are present . This fact raises several ethical debates: the age at which an individual is considered mature enough to choose testing; whether parents have the right to have their children tested; and managing confidentiality and disclosure of test results . </P> <P> There is no cure for HD . Full - time care is required in the later stages of the disease . Treatments can relieve some symptoms and in some improve quality of life . The best evidence for treatment of the movement problems is with tetrabenazine . HD affects about 4 to 15 in 100,000 people of European descent . It is rare among Japanese, while the occurrence rate in Africa is unknown . The disease affects men and women equally . Complications such as pneumonia, heart disease, and physical injury from falls reduce life expectancy . Suicide is the cause of death in about 9% of cases . Death typically occurs fifteen to twenty years from when the disease was first detected . </P>

What is the genetic mutation of huntington's disease
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