Huntington's Disease

What is Huntington's disease?

Huntington's disease (HD) is an inherited disorder that causes nerve cells (neurons) in parts of the brain to slowly break down and die. The disease affects areas of the brain that control voluntary (intentional) movement.

People living with HD develop uncontrollable dance-like movements (chorea), which can affect a person’s fingers, feet, face, or torso. These symptoms can get worse over time or when the person is nervous or distracted.

Some people also develop dystonia, in which muscles tighten without control and cause the body to become stuck in unusual positions. They may also have problems with behavior, mood, and thinking.

Symptoms of HD usually appear in middle-aged people (adult HD). Children may also experience HD (juvenile HD), but it’s rare.

Symptoms of HD

Early symptoms of HD can vary from person to person, but often include:

Changes in thinking may include:

• Problems with attention or judgment
• Trouble solving problems or making decisions
• Difficulty with driving
• Trouble organizing or prioritizing (deciding which things are most important to do)
• Problems learning or remembering new things, putting thoughts into words, or answering a question

These thinking changes get worse over time in people with HD. Eventually, many people with HD are not able to work, drive, or care for themselves. When thinking problems are severe enough to affect daily life, doctors may call this dementia. But many people with HD stay aware of their surroundings and can express their feelings.

Changes in behavior include: 

• Mood swings or feeling easily annoyed (irritable or cranky)
• Feeling uninterested, depressed, or angry
• Thoughts of suicide, severe depression, or loss of touch with reality (psychosis)
• Pulling away from friends and family

Everyone experiences HD differently, and some symptoms may change as the disease progresses.

Who is more likely to get Huntington's disease?

HD is an inherited (genetic) disorder. It’s passed down from parent to child through a genetic variant (a change in a particular gene). 

Genetic risk

When a parent has HD, each child has a 50% chance of inheriting the genetic variant. If a child does not inherit the variant, they won’t develop the disease and can’t pass it on to future generations.

HD is caused by a change in the gene that makes the protein huntingtin (HTT). This change causes a section of DNA called CAG to repeat itself many more times than normal, causing production of an abnormal version of huntingtin that damages brain cells.

Genetic risk for HD varies depending on the number of CAG repeats a person has. 

• Most people have fewer than 27 CAG repeats in their HD gene, so they aren’t at risk for the disease. 
• People who have CAG repeats in the middle range (27 to 35) aren’t likely to develop the disease, but they could still pass it on to future generations. 
• People with HD may have 36 or more CAG repeats.

How is Huntington's disease diagnosed and treated?

Doctors diagnose HD based on a person's symptoms, neurological and lab tests, brain imaging family history, and genetic testing. A specialist that works with disorders of the brain and nervous system (neurologist) may check reflexes, balance, movement, muscle strength, hearing, walking, thinking, memory, and mood.

Doctors may also refer people with HD to specialists who can help diagnose and manage symptoms, including mental health professionals, genetic counselors, and speech-language therapists.

Genetic testing

Genetic testing can confirm or rule out inherited conditions like HD and help determine a person's chance of developing or passing on the disease. 

The most accurate way to test for HD is to count the number of CAG repeats in a person’s HTT gene using DNA from a blood sample. People who have 36 or more repeats have HD. People with less than 26 repeats don’t have the condition. Prenatal testing is an option for people who have a family history of HD and are concerned about passing the disease to a child. 

Brain scans

Although genetic testing is the best way to confirm a diagnosis of HD, a doctor may use brain scans such as magnetic resonance imaging (MRI) or computed tomography (CT) to look for changes in the brain. As HD gets worse, these scans may show certain parts of the brain shrinking, but these changes can also happen in other conditions, and people with early HD may have normal scans.

Learn more about neurological diagnostic tests and procedures.

Treating HD

There is no treatment that can stop or reverse HD, but some of the symptoms can be treated:

• The medicines tetrabenazine, deuterabenazine, and valbenazine treat chorea symptoms by affecting brain signals that control body movement. 
• Antipsychotic medicines, such as risperidone and olanzapine, may help calm chorea movements and also treat psychiatric symptoms such as severe irritability, unusual thoughts, or seeing or hearing things that aren't there. Some antipsychotic medicines can make movement-related symptoms worse in people with HD, so doctors monitor for side effects and adjust treatment as needed. 
• Medicines can also be used to treat depression and anxiety in people with HD.

Side effects of medicines used to treat the symptoms of HD may include tiredness, sleepiness, trouble concentrating, restlessness, or increased activity.

What are the latest updates on Huntington's disease?

The National Institutes of Health (NIH), which includes NINDS, is the leading federal funder of research on the brain and nervous system, including disorders such as HD. NIH supports new research to better understand, diagnose, and treat HD.

Understanding HD

NIH-funded research projects are studying how the abnormal huntingtin protein damages and destroys brain cells. Some researchers are looking at how abnormal huntingtin travels through the brain and how brain immune cells called glia may be involved. Other research is studying why some brain cells in an area of the brain called the striatum are especially vulnerable to abnormal huntingtin. This research could lead to ways to prevent and treat HD. 

Researchers are also studying how the HDD CAG repeat changes over a person's lifetime. In some people with HD, the number of CAG repeats increases over time. This may contribute to symptoms starting earlier and worsening faster. Slowing or stopping this expansion might be a way to keep the disease from getting worse.

Researchers are also studying how the brain clears away unwanted materials and how blood vessel function may contribute to HD.

Treatments

NINH-funded scientists are looking for new treatments for HD. Many are working on ways to lower the amount of abnormal huntingtin protein in the brain, including using molecules that can switch off the huntingtin gene. 

Other researchers are developing ways to deliver proteins that help protect brain cells directly to areas of the brain affected by HD. Researchers are also developing better ways to deliver experimental therapies that target the HD-causing gene directly to the brain. 

Biomarkers

Biomarkers are biological signs of disease that can be found and measured in brain images, blood, and spinal fluid. They can show whether a person has a disease or condition and how it's changing over time.

NIH-funded researchers are looking for biomarkers to track HD before and after symptoms begin. This information could help doctors diagnose HD earlier and also better measure whether a treatment is working in a clinical trial.

Recent clinical trials

NIH supports clinical trials to learn more about how HD develops before and after symptoms begin. The PREDICT-HD study followed more than 1,000 people who have the HD gene variant but had not been diagnosed with the disease. The scientists looked at brain scans and took measurements of thinking, memory, and movement over a period of several years. This work showed that measurable brain and behavioral changes can be detected up to 15 years before an HD diagnosis. That’s important information for understanding the condition and also for designing clinical trials to test treatments. 

An NIH-supported study is tracking brain changes in children, teens, and young adults ages 6 to 30 who have a parent or grandparent with HD. The researchers hope to understand how HD affects the developing brain and to identify early biomarkers specific to juvenile HD.

For more information on research about HD, check NIH RePORTER, a searchable database of current and past research projects funded by NIH and other federal agencies. RePORTER also has links to publications and resources from these projects. 

For research articles and summaries on HD, search PubMed, which contains citations from medical journals and other sites.

How can I or my loved one help improve care for people with Huntington's disease?

Consider participating in a clinical trial so clinicians and scientists can learn more about dystonia and related disorders. Clinical research with human study participants helps researchers learn more about a disorder and perhaps find better ways to safely detect, treat, or prevent disease.

All types of participants are needed—those who are healthy or may have an illness or disease—of all different ages, sexes, races, and ethnicities. This helps make sure that study results apply to as many people as possible and that treatments will be safe and effective for everyone who will use them.

For information about participating in clinical research, visit the NINDS Clinical Trials site and NIH Clinical Research Trials and You. Learn about clinical trials currently looking for people with HD at ClinicalTrials.gov, a searchable database of current and past clinical studies and research results.