What is Huntington’s disease?
Huntington’s disease, which is sometimes called Huntington’s chorea, is a progressive neurological condition that attacks the brain, leading to a loss of physical and mental functions. Huntington’s disease can be extremely frightening because of the startling transformations people with Huntington’s disease undergo and the grim prognosis. But the support of a community of patients and families living with Huntington’s disease is among the most active in the United States, and they are vocal in the cause of raising awareness and searching for a cure.
Huntington’s disease is exceedingly rare, and primarily affects people of European ancestry. It’s estimated that three to seven of every 100,000 people will have the disease.
Most Huntington’s disease cases are classified as “adult-onset,” with diagnosis typically occurring in the 30s or 40s; lifespan after signs and symptoms first appear ranges from 15 to 20 years. There is an even rarer form of juvenile Huntington’s disease that shares many characteristics and symptoms of adult-onset, but its impact is arguably more virulent and has a shorter lifespan of 10 to 15 years.
What causes Huntington’s disease?
Huntington’s disease is caused by a mutation in the HTT gene. The HTT gene sends instructions to create the protein huntingtin. Scientists don’t know the exact purpose of huntingtin, but it appears to be involved in the health and function of neurons (nerve cells) in the brain. The mutation in the HTT gene is responsible for a buildup of an abnormally long and toxic chain of huntingtin protein, which in turn breaks down into smaller chunks that bind to neurons. As a result, the neurons steadily lose function and die off.
How is Huntington’s disease passed on?
Huntington’s disease is an inherited condition passed from one generation to the next. In order to inherit the HTT gene, at least one parent has to be a carrier. Each child of a carrier parent has a 50/50 chance of inheriting the gene; that child in turn has a 50/50 chance of passing the gene to their children. Children born without the gene will not pass it on to their children.
Genetic testing is available, but the decision to test or not to test can be tough for families with a history of Huntington’s disease. Some prefer to live in the moment and not get tested, feeling that the certainty of knowing won’t change their outcome but will change their outlook. Others want to eliminate the uncertainty so they can plan for their future. Prenatal testing is also available.
What are the symptoms of Huntington’s disease?
There are three distinct categories of Huntington’s disease symptoms:
- Emotional problems: Can include personality changes, mood swings, anxiety, depression, impulsive behaviors
- Cognitive (thinking ability) decline: Can include poor decision-making, forgetfulness, problems retaining or learning new information
- Uncontrolled motor (movement) symptoms: Can include twitching, shrugging, walking and coordination problems, swallowing problems
One of the most common and noticeable of these is a motor symptom called “chorea.” Chorea is an uncontrolled jerking or twitching movement that may worsen as the disease progresses. The term “chorea” comes from a Greek word meaning “dance”; in the past, the random movements from chorea were sometimes called the “Huntington’s Dance.”
Early signs like irritability and depression may not immediately stand out as Huntington’s symptoms, or may be confused with other conditions. Other early signs to be aware of include subtle movements like head jerks or shoulder shrugs, coordination problems, or behavioral changes or learning difficulties.
What treatments are available for Huntington’s disease?
There is currently no cure and no way to reverse the damages caused by Huntington’s disease. Instead, the focus is on symptom management. Some doctors try to suppress the movements of chorea using antipsychotic drugs and dopamine-depleting drugs like reserpine and tetrabenazine—though only tetrabenazine is FDA-approved specifically for chorea. Doctors will also prescribe antidepressants, neuroleptics, or antiepileptic drugs depending on the individual patient’s symptoms and disease stage.