What Is Huntington's Disease?
Huntington's disease is a progressive brain condition that causes uncontrolled movements, emotional problems, and cognitive difficulties.
Huntington's disease is also called:
- Huntington disease
- HD
- Huntington chorea.
Huntington's disease affects an estimated 3 to 7 per 100,000 people of European ancestry. The condition appears to be less common in other populations, such as African Americans.
In the United States alone, about 30,000 people have Huntington's disease; about 1 in every 10,000 people is thought to have the condition. At least 150,000 other people have a 50 percent risk of developing it, and thousands more of their relatives live with the possibility that they, too, might develop HD.
Huntington's disease typically begins in middle age. This form is called adult-onset Huntington's disease. There is also an early-onset form (
juvenile Huntington disease) that begins in childhood or adolescence.
What Causes Huntington's Disease?
The disease is caused by a defect in a gene on chromosome number 4. This gene is known as the Huntington disease (HD) gene.
Huntington's disease is almost always an inherited disease, passed from parent to child through a genetic mutation. Each child of a parent with the condition has a 50-50 chance of inheriting the Huntington disease gene.
If a child does not inherit the Huntington disease gene, he or she will not develop the condition and cannot pass it to subsequent generations.
A person who inherits the HD gene will sooner or later develop Huntington's disease. Whether one child inherits the gene has no bearing on whether others will or will not inherit it.
Not all cases of Huntington's disease are inherited; 1 to 3 percent of cases are sporadic, meaning they occur even though there is no family history.
Huntington's Disease Symptoms
Early symptoms of Huntington's disease may include:
- Mood swings
- Depression
- Irritability
- Trouble driving, learning new things, remembering a fact, or making a decision.
As the disease progresses, concentration on intellectual tasks becomes increasingly difficult, and people may have difficulty feeding themselves and swallowing.
Some of the symptoms for juvenile Huntington's disease differ from those of the adult-onset form.
Experienced neurologists can make a Huntington's disease diagnosis. In order to diagnose the condition, the doctor will usually ask a number of questions (including those concerning personal and family medical history), perform a physical exam, and recommend certain tests, including a genetic test.
Huntington's Disease and Genetic Testing
The discovery of the Huntington disease gene has led to a genetic test to make or confirm the diagnosis.
The same genetic test is also available as a screening procedure, which allows people to be tested for the disease even if they have no symptoms of Huntington's disease.
Using a blood sample, the genetic test analyzes DNA for the mutation by counting the number of CAG repeats in the Huntington disease gene. Individuals who do not have HD usually have 28 or fewer repeats. Individuals with the condition usually have 40 or more repeats
(see Genetics of Huntington's Disease for more information).
Treating Huntington's Disease
There is no cure for Huntington's disease. Therefore, treatment usually involves managing the symptoms associated with the disorder. Treatment also focuses on lifestyle and care issues.
This supportive treatment often includes such things as:
- Speech therapy
- Regular physical activity
- Assistance with feeding-related issues
- Proper nutrition
- Adequate fluids.
Support for People With Huntington's Disease
Individuals and families affected by Huntington's disease can take steps to ensure that they receive the best advice and care possible. Physicians and state and local health service agencies can provide information on community resources and family support groups that may exist.
Possible types of help for people with Huntington's disease include:
- Legal and social aid
- Home care services
- Recreation and work centers
- Group housing
- Institutional care.
The rate of progression, as well as the age when symptoms of Huntington's disease appear vary from person to person. Adult-onset Huntington's disease most often begins in middle age. Individuals with
juvenile Huntington disease develop symptoms when they are young -- before age 20.
In general, the duration of the disease ranges from 10 to 30 years. The most common causes of death are infection (most often pneumonia), injuries related to a fall, or other complications.
At this time, there is no way to stop or reverse the course of Huntington's disease.
History of Huntington's Disease
In 1872, the American physician George Huntington wrote about an illness that he called "an heirloom from generations away back in the dim past." He was not the first to describe the disorder, which has been traced back at least to the Middle Ages. One of its earliest names was chorea, which, as in "choreography," is the Greek word for dance.
The term chorea describes how people affected with the disorder writhe, twist, and turn in a constant, uncontrollable dance-like motion. Later, other descriptive names evolved. "Hereditary chorea" emphasizes how the disease is passed from parent to child. "Chronic progressive chorea" stresses how symptoms of the disease worsen over time. Today, physicians commonly use the simple term "Huntington's disease" to describe this highly complex disorder.
