Huntington's disease (HD), also known as Huntington's chorea, is an inherited disorder that results in the 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.
HD is typically inherited, 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.
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.
The first likely description of the disease was in 1841 by Charles Oscar Waters. The condition was described in further detail in 1872 by the physician George Huntington, after whom it is named. The genetic basis was discovered in 1993 by an international collaborative effort led by the Hereditary Disease Foundation. Research and support organizations began forming in the late 1960s to increase public awareness, to provide support for individuals and their families, and to promote research. Current research directions include determining the exact mechanism of the disease, improving animal models to aid with research, testing of medications to treat symptoms or slow the progression of the disease, and studying procedures such as stem cell therapy with the goal of repairing damage caused by the disease.