Huntington’s disease (HD) is a progressive neurodegenerative disease that is passed on genetically from parents to children. In HD, the person’s brain cells begin to degenerate, causing physical, cognitive and emotional problems. Classic symptoms include dementia, uncontrollable writhing movements and often a lack of insight into behavior.
As many as 250,000 people in the United States have or will develop HD. Symptoms usually begin between the ages of 30 and 50, although juvenile HD targets children as young as 2. It has also been seen in people as old as 80, but that's rare. Typically, the younger a person is when the symptoms begin, the faster the disease progresses. Males and females are equally likely to develop the condition.
Symptoms of Huntington’s Disease
- Early Stage HD: Early symptoms of HD include difficulty learning new things or making decisions, problems with driving, irritability, mood swings, involuntary movement or twitching, coordination and short-term memory problems.
- Middle Stage HD: As HD progresses into the middle stage, the person has trouble with swallowing, speaking, walking, memory and concentrating on tasks. The writhing movements (called chorea) of HD may become very pronounced and interfere significantly with daily functioning. The person may also develop some obsessive behaviors.
- Late Stage HD: Late stage HD symptoms consist of the inability to walk or talk, and require full care from a caregiver. People who have late stage HD are at high risk for choking.
What Causes Huntington’s Disease?Almost all cases of HD are hereditary, meaning that the disease is inherited from parents. If your father or mother has HD, you have a 50% chance of having the HD gene. If you inherited the HD gene, you will at some point develop HD. If you did not inherit the HD gene, you will not develop HD nor will you pass the gene on to your children.
Approximately 1% to 3% of those with HD do not have a parent with HD. In that case, the disease can’t be traced to someone else in the family.
Scientists identified the HD gene in 1993. Some people at risk for HD get their blood tested to determine if they are a carrier of the gene, while others forgo the testing since there is no effective treatment for the disease at this time.
How is Huntington’s Disease Different from Alzheimer’s Disease?HD and Alzheimer’s symptoms initially are quite similar, although HD’s average age of onset (30 to 50 years) is much younger than Alzheimer’s disease, where the majority of cases develop in those who are older than 65. Both diseases cause dementia and affect memory, decision-making skills and the ability to learn new things.
As HD progress, people display the disease's classic writhing movements; in Alzheimer’s, a person’s ability to move usually becomes gradually more difficult, but they don’t usually experience many involuntary movements. In late stage HD, people can usually still comprehend what others are saying to them, and family and friends may remain familiar to them. In late stage Alzheimer’s, most people are unable to understand others and do not appear to be aware of others around them.
Additionally, almost all cases of HD are inherited, while most Alzheimer’s cases are not directly inherited.
Treatment of Huntington’s DiseaseThere is no cure for Huntington’s disease, but the symptoms of involuntary movements can be treated with tetrabenazine, the only drug approved (in 2008) by the U.S. Food and Drug Administration for the condition. Other medications similar to those used in Alzheimer’s can be used to treat HD's cognitive, behavioral and emotional symptoms. In addition, drugs such as haloperidol (Haldol) and olanzapine (Zyprexa) are often used.
Exercising - through formal methods like physical and occupational therapy, and informal ways such as walking and remaining active - has also proven helpful in slowing the decline that HD causes.
Preventing Huntington’s DiseaseThere currently is no way to prevent HD. However, maintaining an active body and a healthy mind probably helps delay symptoms or slows progression.
Prognosis of Huntington’s DiseaseThe prognosis of HD is poor at this time. The average life expectancy following diagnosis ranges from 10 to 20 years. Death usually results from complications of HD, such as choking or the inability to fight an infection like pneumonia. However, since the gene responsible for passing HD on has been identified, researchers are targeting this disease by studying the effects on the brain, with the goal of reversing the damage. There are also ongoing clinical trials to test medications and other treatment methods.
Alzheimer's Society. Rarer Causes of Dementia. Accessed December 29, 2011. http://www.alzheimers.org.uk/site/scripts/documents_info.php?documentID=135
Huntington’s Disease Society of America. Stages of Huntington’s Disease. Accessed December 27, 2011. http://www.hdsa.org/living-with-huntingtons/family-care/stages-of-hd.html
Huntington’s Disease Society of America. What Is Huntington’s Disease. Accessed December 27, 2011. http://www.hdsa.org/about/our-mission/what-is-hd.html
National Institute of Neurological Disorders and Stroke. National Institute of Health. NINDS Huntington's Disease Information Page. Accessed December 21, 2011. http://www.ninds.nih.gov/disorders/huntington/huntington.htm