Huntington's Disease

What is Huntington's Disease
Huntington's disease (HD) is a devastating hereditary brain disorder that affects men and women equally across all ethnic and racial lines, passed from parent to child through a mutation in one single gene called huntingtin. Each child of an HD parent has a 50-50 chance of inheriting the HD gene and will sooner or later develop the disease. However, age of onset of clinical symptoms of Huntington disease is quite variable, although the disease starts in the majority of cases in midlife between the ages 35 and 45. HD is a degenerative disease whose symptoms are caused by the loss of cells in a part of the brain called the basal ganglia. Clinical symptoms are characterized by a rapidly progressive alteration of motor abilities (chorea, bradykinesia), psychological disturbances (depression and irritability) and cognitive impairment (of most functions by the later stages) leading to dementia. Persons with HD become eventually totally dependent upon others. A genetic test, coupled with a complete medical history and neurological and laboratory tests, helps physicians diagnose HD. Presymptomic testing is available for individuals who are at risk for carrying the HD gene.

HD prognosis
Although much has been learned about the causes and effects of HD in the last twenty years there is at present no preventative or curative therapy available. Furthermore, current symptomatic treatment is very limited and often inadequate. Medications can relieve only some symptoms in certain individuals. 

HD biology
The disease is caused by an autosomal dominant mutation in either of an individual's two copies of the huntingtin gene. The Huntingtin Gene was found to contain a specific section that is expanded in people with HD. In all people, this stretch of genetic material, or DNA, contains a pattern of so-called "trinucleotide repeats". In most people, the repeated pattern "CAG" occurs 30 times or less. In HD, it occurs more than 36 times. This abnormal protein is toxic to the neurons of the striatum and other regions of the brain. By analyzing a person's DNA and counting the number of CAG's, it is possible to tell if that person will develop HD. The test cannot predict the age of onset, but the juvenile form has normally more than 50 repeats upto more than 120.


Please go to LINKS for a list of websites providing more detailed information on HD and contact information of patient associations.