Huntington’s Disease
Huntington’s Disease (HD) – also called Huntington’s Chorea – is an inherited disorder of the central nervous system. It causes progressive deterioration with varying symptoms which may include involuntary movements, speech impairment, and intellectual and emotional changes. 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
It was estimated from a survey carried out by Dr. Morrison in Belfast (1992) that perhaps 400 people have the illness in the Republic of Ireland. Professor Andrew Green of the National Centre for Medical Genetics believes the incidence in the Republic of Ireland is more common and that there are at least 400-500 people affected. On average for every individual with the disease there are 22 close family members indirectly affected. Therefore over 9000 family members may require support and information.
Genetic Test
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 HD patients
There is no cure for HD at present. It is possible to treat some of the effects, such as depression, and involuntary movements, with various drugs. Improvements in general health, such as adequate nutrition, will bring about improvements in the status of the person, and in their enjoyment of life. It is recommended that HD patients should have 5000 kcals per day to maintain weight stability
