Huntington's Disease
Huntington's disease, chorea, or disorder (HD), is a neurodegenerative genetic disorder that affects muscle coordination and leads to cognitive decline and dementia. It typically becomes noticeable in middle age. HD is the most common genetic cause of abnormal involuntary writhing movements called chorea.
Symptoms of the disease can vary between individuals and among affected members of the same family, but the symptoms progress predictably for most individuals. The earliest symptoms are a general lack of coordination and an unsteady gait. As the disease advances, uncoordinated, jerky body movements become more apparent, along with a decline in mental abilities and behavioral and psychiatric problems. Physical abilities are gradually impeded until coordinated movement becomes very difficult. Mental abilities generally decline into dementia. Complications such as pneumonia, heart disease, and physical injury from falls reduce life expectancy to around twenty years after symptoms begin. There is no cure for HD, and full-time care is required in the later stages of the disease. Emerging treatments can relieve some of its symptoms.
It is much more common in people of Western European descent than in those of Asian or African ancestry. The disease is caused by an autosomal dominant mutation on either of an individual's two copies of a gene called Huntingtin, which means any child of an affected parent has a 50% risk of inheriting the disease. In the rare situations where both parents have an affected copy, the risk increases to 75%, and when either parent has two affected copies, the risk is 100% (all children will be affected). Physical symptoms of Huntington's disease can begin at any age from infancy to old age, but usually begin between 35 and 44 years of age. About 6% of cases start before the age of 21 years with an akinetic-rigid syndrome; they progress faster and vary slightly. The variant is classified as juvenile, akinetic-rigid or Westphal variant HD.
Self-help support organizations, first founded in the 1960s and increasing in number, have been working to increase public awareness, to provide support for individuals and their families, and to promote research. The Hereditary Disease Foundation, a research group born out of the first support organization, was instrumental in finding the gene in 1993. Since that time, every few years new research discoveries have been made and understanding of the disease is improving. Current research directions include determining the exact mechanism of the disease, improving animal models to expedite research, clinical trials of pharmaceuticals 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.
LINKS
ww.mayoclinic.com/health/huntingtons-disease/DS00401