Huntington’s Disease (HD) is a hereditary neurological disorder that causes brain cell degeneration leading to deterioration of the physical, cognitive and emotional self. Within the same family symptoms can vary and may include involuntary movements, speech impairment, difficulties planning and organising tasks and changes in motivation. Symptoms usually appear between the ages of 30 and 45, although they may appear earlier or later.
HD is a genetic disorder
HD is passed from one generation to the next because of an alteration in one of the many genes each of us inherits from our parents. The gene that causes HD is called an autosomal dominant gene. This means that if either parent has the altered HD gene, each son and daughter has a 50/50 chance of inheriting or not inheriting HD. People with the abnormal gene will always develop the disease, unless they die of other causes prior to developing signs and symptoms.. People who do not inherit the HD gene will not develop the disease, neither will their children, or their children’s children. The disease does not “skip a generation”.
How does the disease get its name?
The disease is named after Dr. George Huntington, an American physician, who was the first to publish a precise description of the symptoms and course of the disease in an article written in 1872.
Prevalence of HD
Professor Patrick Morrison conducted a survey in Northern Ireland in 2001 which estimated the prevalence of 10-16 people per 100,000 (Lancet Neurology). His analysis of more recent data suggests a prevalence of 14-16 per 100,000. Based on the Republic of Ireland population of 4,670,976 (July 2011) this would indicate approximately 700 people with HD and a further 3000 at risk.
The gene which when altered causes HD was isolated in March 1993. The abnormality which causes HD is an expansion of the DNA sequence of an otherwise normal gene.
Diagnostic and predictive testing
A diagnostic test is used to confirm the diagnosis of HD in a person showing symptoms and signs of the disease. The test is carried out to confirm a clinical likelihood that a person already has HD.
A predictive test for HD is carried out in a healthy person, who has no signs or symptoms of HD, but who has a family history of HD. Not everyone with a family history of HD wishes to pursue a predictive genetic HD test, and having the test remains an individual choice.
Details on predictive testing are available from the National Centre for Medical Genetics - Tel: (01) 409 6739, Website: www.genetics.ie
Care of People with HD
While there is no cure for HD at present a clear multidisciplinary treatment plan can help to maintain a person's quality of life. Input from rehabilitative therapists such as physio, speech and language, occupational therapists, dieticians etc is necessary to manage physical symptoms. Maintaining a healthy body weight is essential because people who are under weight lose muscle mass and therefore feel weaker, become more apathetic or depressed and are more prone to catching infections. Exercise, social and psychological support can help maintain a persons mental well-being. Medication should be reviewed regularly to ensure it remains effective in treating symptoms over the course of the illness.
For more detailed information see the HD Handbooks on the Information page.