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Huntington’s disease: symptoms, heredity

by Josephine Andrews
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Huntington ‘s disease (Huntington’s disease, formerly: St. Vitus’ dance) is an inherited disease that affects the brain. The disease leads to the gradual destruction of certain areas of the brain. Typical symptoms of Huntington’s disease are movement disorders as well as cognitive and psychiatric disorders. Huntington’s disease is caused by a faulty gene. Read more about Huntington’s disease.

ICD codes for this disease:

ICD codes are internationally valid codes for medical diagnoses. They can be found, for example, in doctor’s letters or on certificates of incapacity for work.

G10

quick overview

  • Symptoms: Movement disorders such as involuntary, jerky movements, falls, swallowing and speaking disorders, personality and behavior changes, depression, delusions, loss of intellectual abilities
  • Course of the disease and prognosis: The disease continues to progress over the years. Those affected usually die from complications resulting from the disease.
  • Causes and risk factors: A genetic defect leads to the formation of a defective protein that accumulates in the nerve cells and damages them. The origin of the disease is not yet fully understood.
  • Diagnosis: family history, neurological examination, evidence of gene mutation
  • Treatment: There is no known causal therapy. Treatment aims to relieve symptoms, eg through medication, physiotherapy and occupational therapy as well as measures to improve speech and swallowing disorders.
  • Prevention: There is no way to prevent it. If you want to have children, a genetic test from parents who are at risk helps to determine how likely they are to pass the disease on to their children. The test requires careful consideration of the emotional distress of the individual.

What is Huntington’s disease?

Huntington’s chorea (also known as Huntington’s disease) is a very rare hereditary disease of the brain. In studies of the frequency of Huntington’s disease, researchers estimate that about seven to ten out of 100,000 people in western Europe and North America are affected.

Huntington’s disease occurs at any age, but tends to increase at certain ages. The first symptoms of Huntington’s disease often appear between the ages of 35 and 45, more rarely in early childhood or only in old age. This also depends on where exactly the disease-triggering change (mutation) is located in the genome.

Typical symptoms of Huntington’s disease are movement disorders and mental disorders, such as changes in personality and a decrease in intellectual abilities through to dementia .

The possibilities of influencing the course of Huntington’s disease are limited. Researchers have tested a large number of substances designed to protect nerve cells (neurons) and stop the progressive neuron death. So far, none of these substances has shown a clear effect on the course of the disease.

The therapy therefore focuses on alleviating the symptoms of Huntington’s disease.

There are support groups that help people with Huntington’s disease and their families.

Where did the name Huntington’s Chorea come from?

The disease used to be known as St Vitus’ dance. The term comes from the Middle Ages. Since the disease is accompanied by jerky, uncontrollable movements, the association with a dance aroused her. Hence the first part of the name. Because the Greek word for “dance” is “choreia”.

The second part of the name, Huntington, goes back to US doctor George Huntington, who first described the disease in 1872 and recognized that Huntington’s disease is inherited.

Today’s terms for Huntington’s disease are Huntington’s disease or Huntington’s disease.

What are the symptoms of Huntington’s disease?

Huntington’s disease: initial stage

Huntington’s disease often begins with non-specific symptoms. The first signs are, for example, psychological abnormalities that continue to progress. Many patients are increasingly irritable, aggressive, depressed or uninhibited. Others feel a loss of spontaneity or an increase in anxiety.

The movement disorders in Huntington’s disease consist of sudden, involuntary movements of the head, hands, arms, legs or trunk. In extreme cases, this leads to a prancing gait typical of the disease. This is why Huntington’s disease used to be called “St. Vitus’ dance”.

People with Huntington’s disease are often initially able to incorporate these exaggerated and unwanted movements into their movement patterns. This gives the observer the impression of exaggerated gestures. In many cases, those affected do not initially notice their movement disorders as such.

Huntington’s disease: later stages

If Huntington’s disease progresses, the tongue and throat muscles are also affected. Speech seems choppy, sounds are expelled explosively. Swallowing disorders are also possible. Then there is a risk that those affected will choke, food will get into the airways and, as a result, pneumonia will develop.

As Huntington’s disease progresses, patients gradually lose their mental abilities. After about 15 years, dementia can be detected in almost all those affected.

In the final phase of Huntington’s disease, patients are usually bedridden and completely dependent on the help of others.

Huntington’s disease – similar diseases

Symptoms similar to those of Huntington’s disease sometimes exist with other non-hereditary causes. Examples are the consequences of infectious diseases or a hormonal change during pregnancy (chorea gravidarum). Medications and hormonal contraceptives such as the pill are rarer triggers.

In addition, in rare cases, strokes cause similar symptoms in certain regions of the brain. Due to circulatory disorders in the brain , a form of chorea sometimes occurs in old age. Doctors suspect that diseases such as an overactive thyroid are also linked to a chorea-like disease.

In contrast to Huntington’s disease, the course of these forms is not progressive. The movement disorders usually regress. Severe psychological symptoms are atypical in such cases.

What is the prognosis and life expectancy for Huntington’s disease?

Huntington’s disease cannot be cured. The life expectancy for Huntington’s disease depends, among other things, on the age at the onset of the disease. On average, those affected live with the disease for about 15 to 20 years after diagnosis. However, since the course of the disease varies individually, life expectancy is higher or lower in individual cases.

Since the cause of Huntington’s disease cannot be treated, the disease continues to progress. Ultimately, people with end-stage Huntington’s disease usually die from complications that arise as a result of Huntington’s disease. A feared complication is pneumonia, for example. This occurs, for example, when food particles get into the trachea due to swallowing disorders.

How does Huntington’s disease progress?

The symptoms that those affected develop and how well they respond to the various medications vary greatly. Only specialists who deal with Huntington’s disease on a daily basis are sufficiently familiar with the many peculiarities of the disease.

It is advisable for HD patients to be examined regularly in one of the HD centers in Germany in order to adapt the individual therapy to the current course of the disease.

For relatives and life partners of people with Huntington’s disease, the disease is also very stressful, both emotionally and sometimes financially. The Deutsche Huntington Hilfe eV (https://dhh-ev.de/) is available to families of those affected with valuable advice and important addresses.

How is Huntington’s disease inherited?

Huntington’s disease is caused by a genetic defect. As a result, nerve cells in certain areas of the brain die. The condition affects both men and women because the gene responsible is not inherited in a sex-linked manner. So it is not on the sex chromosomes X and Y, but on the other chromosomes , the so-called autosomes. There are two copies of each autosome, one from the mother and one from the father.

Inheritance in Huntington’s disease

If a parent has the defective gene, the child has a 50 percent risk of getting the defective gene and developing Huntington’s disease. Experts speak of an autosomal dominant inheritance. Dominant means that the disease breaks out even if the corresponding gene is changed on only one of the two paired chromosomes.

Inheritance of Huntington’s disease – defect on chromosome four

The molecular alphabet of the genetic material (deoxyribonucleic acid, DNA or DNA for short) consists of four nucleic acids: adenine, thymine, guanine and cytosine. Ever new combinations of these four letters form the entire genetic information, which is stored in the form of thread-like structures, the so-called chromosomes.

In Huntington’s disease, a gene on chromosome four is altered. This is the huntingtin gene (HTT gene). It was identified in 1993. The protein huntingtin, which is encoded by this gene, does not work properly. This eventually leads to the symptoms of Huntington’s disease.

In healthy people, the three nucleic acids cytosine-adenine-guanine (CAG for short) are repeated 10 to 30 times in this area on chromosome four. If there are more than 36 CAG repeats (CAG repeats or CAG triplets), Huntington’s disease breaks out. 30 to 35 CAG repeats are considered gray area.

In about one to three percent of those affected, no blood relative to Huntington’s disease can be found. Either it is a completely new gene change, a so-called new mutation, or one of the parents of the HD patient already had 30 to 35 repetitions and the disease did not break out in him.

The more CAG repeats are counted on chromosome four, the earlier Huntington’s disease breaks out and the faster the disease progresses. In the next generation, the number of CAG repeats often increases. At more than 36, the children develop Huntington’s disease.

The nerve cell death in Huntington’s disease affects the cerebral cortex and especially the so-called stem ganglia. These are large clusters of nerve cells inside the two hemispheres of the brain, which, among other things, play a role in the coordinated sequence of movements.

How is Huntington’s disease diagnosed?

If Huntington’s disease is suspected, it is advisable to visit a specialized Huntington’s center with appropriately experienced neurologists. Huntington’s disease is rare. Family doctors and sometimes even “normal” neurologists may therefore never have seen a patient with this disease.

At the beginning of the diagnosis of Huntington’s disease, there is a detailed questioning about the medical and family history ( anamnesis ). It is interesting for the doctor whether close relatives (parents, grandparents) are suffering from Huntington’s disease. Important for the diagnosis are the Huntington’s Chorea symptoms, the course and abnormalities in the neurological examination.

blood test . The excessive number of repeats of the same base pairs (CAG) in a specific gene on chromosome four can be detected using molecular genetic testing.

If no genetic change can be found, blood is taken again to rule out diseases that initially show symptoms similar to Huntington’s disease. Among other things, thyroid values ​​​​and the concentration of antibodies that are directed against endogenous substances (so-called autoantibodies ) are determined.

determine nerve damage

To determine the extent of nerve damage, people with Huntington’s disease have neurological, neuropsychological, and psychiatric evaluations. These examinations are carried out either by experienced doctors or specially trained neuropsychologists.

Imaging studies such as computed tomography (CT) or magnetic resonance imaging (MRI) of the brain can show the breakdown of individual brain areas that are particularly affected by Huntington’s disease. Electrophysiological diagnostics examines brain function and, in individual cases, also provides important information on Huntington’s disease .

Genetic test for Huntington’s disease

Healthy people with an increased risk of Huntington’s disease can also have a genetic test. Doctors speak of predictive diagnostics or predictive diagnostics. With this test, it is possible to clearly determine whether someone will develop Huntington’s disease or not.

However, knowing that you are a carrier of this genetic modification has a massive impact on the psyche of those affected. Therefore, there are guidelines for performing a genetic test for Huntington’s disease. Among other things, the persons concerned must be informed in advance about the risks.

Genetic testing is not permitted for minors. Even at the request of third parties, no genetic test for Huntington’s disease may be carried out. This means that doctors, insurance companies, adoption agencies or employers, for example, are not allowed to carry out a genetic test if the affected (adult) person does not want to do it themselves.

A genetic test of the unborn child during pregnancy or of the embryo before artificial insemination is prohibited in Germany, since it is a disease that only breaks out after the age of 18. In Austria and Switzerland, however, such prenatal diagnostics or peri-implantation diagnostics is possible in principle.

In exceptional cases – if the onset of the disease is expected before the age of 18 – prenatal genetic diagnosis is also possible in Germany. Those affected should contact their doctor or one of the genetic counseling centers for detailed advice.

What are the treatments for Huntington’s disease?

Huntington’s disease – medication

Huntington’s disease cannot be treated causally and is not curable. However, certain medications relieve symptoms.

For example, doctors use the active ingredients tiapride and tetrabenazine to combat excessive and uncontrolled movements. These agents counteract the body’s own messenger substance dopamine . In the case of depressive moods, antidepressants from the group of selective serotonin reuptake inhibitors (SSRI) or sulpiride are usually used.

There is no official therapy recommendation against the development of dementia in Huntington’s disease. In some studies, the active ingredient memantine slowed mental decline.

In addition to drug therapy for Huntington’s disease, supportive measures such as physiotherapy , ergotherapy and speech therapy are helpful in alleviating the symptoms. For example, special exercises help to improve speech or swallowing disorders.

In addition, the activities of everyday life can be trained with occupational therapy. This enables people with Huntington’s disease to remain independent for longer. Psychotherapy helps many sufferers to better deal with the disease. Self-help groups are also a great source of support for many.

Since many people with Huntington’s disease lose a lot of weight over the course of their disease, a high-calorie diet makes sense. In some cases, being slightly overweight improves Huntington’s disease symptoms.

Huntington’s disease – research

Therapies that stop the underlying degradation process in Huntington’s disease are not yet known. Various new approaches are being pursued in drug therapy for Huntington’s Chorea, but these are still in the experimental stage.

Smaller studies showed slightly positive effects for coenzyme Q10 and creatine. However, larger studies had to be stopped because there was no prospect of effectiveness. Coenzyme Q10 is a protein that occurs naturally in the body and protects cells from damage.

According to studies, another drug tested for the treatment of Huntington’s disease, ethyl icosapent, did not improve movement disorders either.

Can Huntington’s disease be prevented?

As with all hereditary diseases, there is no prevention for Huntington’s disease. To prevent the disease from being passed on to a child, a genetic test provides information on whether a parent is a carrier of the genetic defect.

However, it is important to consider the implications of what a genetic test says. Because the detection of the genetic defect means for those affected that one day they will develop the previously incurable disease Huntington’s Chorea. Detailed advice from a human geneticist is therefore useful for people with a family risk of Huntington’s disease.

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