What Is Huntington’s Disease?
Huntington’s disease is a fatal genetic disorder that causes the progressive breakdown of nerve cells in the brain. It deteriorates a person’s physical and mental abilities usually during their prime working years and has no cure. Every child of a parent with HD has a 50/50 chance of inheriting the faulty gene that causes Huntington’s disease. Today, there are approximately 30,000 symptomatic Americans and 200,000 at-risk of inheriting the disease. In less than 10% of cases, juvenile Huntington’s disease (JHD) affects children & adolescents.
The symptoms of HD are described as having ALS, Parkinson’s and Alzheimer’s diseases – simultaneously.
Symptoms usually appear between the ages of 30 to 50, and worsen over a 10 to 25 year period. Ultimately, the weakened individual succumbs to pneumonia, heart failure or other complications. Everyone has the gene that causes HD, but only those that inherit the expansion of the gene will develop HD and perhaps pass it on to each of their children. Every person who inherits the expanded HD gene will eventually develop the disease. Over time, HD affects the individual’s ability to reason, walk and speak.
- Personality changes, mood swings & depression
- Forgetfulness & impaired judgment
- Unsteady gait & involuntary movements (chorea)
- Slurred speech, difficulty in swallowing & significant weight loss
HD affects the whole brain, but certain areas are more vulnerable than others. Pictured above are the basal ganglia – a group of nerves cell clusters, called nuclei. These nuclei play a key role in movement and behavior control and are the parts of the brain most prominently affected in early HD.
Stages of HD
Although symptoms of HD vary from person to person, even within the same family, the progression of the disease can be roughly divided into three stages.
Early stage HD usually includes subtle changes in coordination, perhaps some involuntary movements (chorea), difficulty thinking through problems and often a depressed or irritable mood. Medications are often effective in treating depression or other emotional problems. The effects of the disease may make the person less able to work at their customary level and less functional in their regular activities at home.
In the middle stage, the movement disorder may become more of a problem. Medication for chorea may be considered to provide relief from involuntary movements. Occupational and physical therapists may be needed to help maintain control of voluntary movements and to deal with changes in thinking and reasoning abilities. Diminished speech and difficulty swallowing may require help from a speech language pathologist. Ordinary activities will become harder to do.
In the late stage, the person with HD is totally dependent on others for their care. Choking becomes a major concern. Chorea may be severe or it may cease. At this stage, the person with HD can no longer walk and will be unable to speak. However, he or she is generally still able to comprehend language and retains an awareness of family and friends. When a person with HD dies, it is typically from complications of the disease, such as choking or infection and not from the disease itself.
In all stages of HD, weight loss can be an important complication that can correspond with worsening symptoms and should be countered by adjusting the diet and maintaining appetite.
The Scope of HD
Approximately 30,000 Americans have HD, but the devastating effects of the disease touch many more. Within a family, multiple generations may have inherited the disease. Those at-risk may experience tremendous stress from the uncertainty and sense of responsibility. In the community, lack of knowledge about HD may keep friends and neighbors from offering social and emotional support to the family, fostering unnecessary isolation. The Huntington’s Disease Society of America has a nationwide network that provides support and referrals for individuals with HD and their families.
HD affects both sexes and all races and ethnic groups around the world.
Who Is At Risk
Every child of a parent with HD has a 50/50 chance of inheriting the expanded gene that causes the disease. If the child has not inherited this expanded gene, he or she will never develop the disease and cannot pass it on to their children.
Genetic Testing & Family Planning
People at-risk for the disease face a difficult choice about genetic testing for HD, given the current absence of an effective treatment or cure. Many people see no benefit in knowing that they will someday develop the disease. Others want an end to uncertainty so that they can make informed choices about the future. The decision whether to test or not is intensely personal and there is no “right” answer.
The Huntington’s Disease Society of America recommends that at risk individuals who are considering genetic testing do so at a genetic testing center that follows the HDSA guidelines. Testing procedures at these centers involves sessions with professionals who are knowledgeable about HD and the local services available. It may take several weeks to receive the results once the genetic test is complete.
Genetic testing for children is typically prohibited before the age of 18, as the child may not understand the full implications of testing and may be vulnerable to pressure from others. However, a child under the age of 18 may be tested to confirm a diagnosis of juvenile onset HD after a thorough neurological exam.
For families wishing to have a child who does not have the gene that causes HD, there are a few options. Pre-genetic diagnostic (PGD) testing can be used with In Vitro Fertilization (IVF) to make sure that any fertilized egg implanted does not have the abnormal gene. This can be done without informing the at-risk patient whether or not they have the gene that causes HD. If a woman is already pregnant, she can receive testing for the fetus with a chorionic villus biopsy at 10-11 weeks or via amniocentesis at 14-18 weeks. Click here to find testing centers near you.
In approximately 10% of cases, HD affects children or adolescents. The symptoms of Juvenile HD (JHD) are somewhat different than adult onset HD and may include stiff or awkward walking, increased clumsiness or changes in speech. The ability to learn new information may decline and the child may lose skills they previous had. JHD typically progresses more rapidly than adult onset HD. Click here to download HDSA’s Juvenile HD Handbook.
An End to HD?
In 1993, researchers identified the gene that causes HD. Since then, research has moved quickly towards developing treatments and, ultimately, a cure. HDSA supports the goals of clinical and basic research at leading research facilities globally. Clinical and observational trials are an important way you can help to sustain the momentum of HD research and move potential new therapies through the approval process. Visit the Research section of the HDSA website for more information and to find a trial in your area. There are opportunities for all HD family members — gene positive, at-risk, gene negative, and caregivers — to participate.