Huntington´s disease: Causes, symptoms, therapy
Huntington´s disease is a condition of the brain that is inherited (Source). In people with Huntington’s condition, areas of the brain that are important for muscle control and mental functions are gradually destroyed (Source). The nerve cells slowly die (Source)and the cause is a defective gene (Source). Read more about Huntington´s disease below.
ICD codes for this condition is G10
Huntington´s disease is a very rare hereditary disease of the brain and is thought to affect seven to ten out of every 100,000 people in Western countries.
Huntington´s disease can break out at any age (Source). The first Huntington symptoms often appear between the ages of 35 and 45, but can also occur in early childhood or only at an advanced age (Source). This also depends on where exactly the disease-triggering change (mutation) lies in the genetic material. Typical symptoms are movement disorders and changes in nature up to dementia.
The possibilities of influencing the course of Huntington´s disease are limited. A large number of substances have been tested which are supposed to protect the nerve cells and stop the progressive neuron destruction. To date, however, none of these substances has had a significant effect on the course of the disease. Nevertheless, there are some drugs available that can alleviate the symptoms of Huntington´s disease.
There are self-help groups that help people with Huntington´s disease and their relatives.
Where the name “Huntington´s disease” comes from
Huntington’s disease goes back to the US doctor George Huntington, who first described the disease in 1872. He had also recognized that Huntington’s disease is inherited. The name comes from the Greek – “choreia” = “dance”. The Huntington’s Chorea has several names: Huntington’s Disease, Huntington’s Disease, or St. Vitus Dance. The reason is that patients gradually lose control over their movements – which can remotely resemble a dance.
Symptoms Of Huntington´s disease
Huntington´s disease: early stages
Huntington’s disease often begins with unspecific symptoms, such as psychological abnormalities, which continue to progress. Many patients are increasingly irritable, aggressive, depressed or uninhibited; others experience a loss of spontaneity or increasing anxiety.
The movement disorders in Huntington’s disease usually consist of sudden, involuntary movements of the head, hands, arms, legs or trunk. In extreme cases, this can lead to a dancing gait typical of the disease. This is why Huntington’s disease used to be called “St. Vitus dance” in Northern European countries.
People with Huntington’s disease can often initially incorporate these exaggerated and unwanted movements into their movement sequences. For the observer, this creates the impression of exaggerated gestures. In many cases, the affected persons do not notice their movement disorders as such at first.
Huntington’s disease: later stages
If Huntington’s disease progresses further, the muscles of the tongue and throat are also increasingly affected. Speech appears choppy, sounds are expelled explosively. Swallowing disorders are also possible – then there is a risk that the affected person will swallow food components and develop pneumonia.
As Huntington’s disease progresses, patients often inexorably lose their mental abilities. After about 15 years, dementia can be detected in almost all affected patients.
In the terminal phase of Huntington’s disease, patients are usually bedridden and completely dependent on the help of others.
Similar Symptoms In Other Conditions
Symptoms similar to those of Huntington’s disease can also be triggered by other, non-hereditary causes. Examples are the consequences of infectious diseases or a hormonal change during pregnancy (Chorea gravidarum). Drugs and hormonal contraceptives (such as the pill) are rarer triggers. This also applies to strokes that affect certain regions of the brain. Due to circulatory disorders in the brain, a form of this condition can also occur in old age.
It is believed that diseases such as hyperthyroidism can also lead to chorea. However, the course of the disease is not progressive, and the movement disorders usually disappear again. Severe psychological symptoms are untypical in such cases.
Causes and Risk Factors Of Huntington’s disease
Huntington’s disease is caused by a genetic breakdown of nerve cells in certain areas of the brain. The disease can affect both men and women because the gene responsible is not inherited in a sex-linked manner – i.e. not on the sex chromosomes X and Y, but on the autosomes. These are the chromosomes that do not determine the sex and are each present in two copies (one from the mother, one from the father).
Each child of a parent carrying the defective gene has a 50% risk of receiving the defective gene and also of contracting Huntington’s disease. Experts speak of an autosomal dominant inheritance. Dominant means that the disease also breaks out if the corresponding gene is altered on only one of the two paired chromosomes.
Heredity – defects on chromosome four
The molecular alphabet of the genetic material (deoxyribonucleic acid, DNA) consists of four nucleic acids: adenine, thymine, guanine and cytosine. 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, one gene on chromosome four is altered (also known as the Huntington gene). It was identified in 1993. The protein encoded by this gene does not function properly, which eventually leads to the symptoms of Huntington’s disease.
In healthy people, the three nucleic acids cytosine adenine guanine repeat 10 to 30 times in this region on chromosome four. If more than 36 cytosine adenine guanine repeats (CAG repeats or CAG triplets), Huntington’s chorea breaks out. 30 to 35 CAG repeats are considered to be grey areas.
In approximately one to three percent of those affected, no blood relative with Huntington’s disease can be found. Either it is a completely new genetic change, a so-called new mutation. Or one parent of the Huntington’s patient has already had 30 to 35 recurrences and the disease did not break out in him. In the next generation, the number of repeats often increases. More than 36 children develop Huntington’s disease.
The more CAG repeats are counted on chromosome four, the earlier Huntington’s disease breaks out and the faster the disease progresses.
The nerve cell death in Huntington’s disease affects the cerebral cortex and especially the so-called stem ganglia. These are large groups of nerve cells inside the two hemispheres of the brain, which play a role in the coordinated flow of movements, among other things.
Diagnosis And Examinations Of Huntington’s Disease
If Huntington’s disease is suspected, it is best to visit a specialized Huntington’s center with appropriately experienced neurologists. This is because family doctors and sometimes “normal” neurologists have never seen a patient with this disease.
At the beginning of the diagnosis of Huntington’s disease there is detailed questioning, including the family history (anamnesis). It is interesting for the physician to know whether close relatives (parents, grandparents) are affected by Huntington’s disease. Important for the diagnosis are also the symptoms of Huntington’s disease (in the early stages they can also indicate other diseases), the course of the disease and abnormalities in the neurological examination.
The diagnosis is confirmed by a blood test. The excessive number of repetitions of the same base pairs (CAG) in a particular gene on chromosome four can be detected by molecular genetic examination.
If no genetic change can be found, blood is taken again to rule out diseases that may initially show similar symptoms to Huntington’s disease. Among other things, thyroid gland values and the concentration of certain autoantibodies (antibodies directed against the body’s own substances) in the blood are determined.
Determination of nerve damage
To determine the extent of the nerve damage, people with Huntington’s disease are also examined neurologically, neuropsychologically and psychiatrically. These examinations are carried out either by experienced doctors or specially trained neuropsychologists.
Imaging examinations such as computer tomography (CT) or magnetic resonance imaging (MRI) of the brain can show the degradation of individual areas of the brain (for example, the so-called tail core and cortex). Electrophysiological diagnostics can also provide important information in individual cases of Huntington’s disease.
Genetic test for Huntington’s disease
Healthy individuals with an increased risk of Huntington’s disease can also have a genetic test performed. Doctors speak of predictive diagnostics or predictive diagnostics. With this test it can be clearly determined whether someone will develop Huntington’s disease or not.
However, this knowledge of being a carrier of this genetic change can have a massive impact on the psyche of those affected. Therefore, there are guidelines for conducting a genetic test for Huntington’s disease. Among other things, the persons concerned must be informed in advance about the risks. No genetic testing may be carried out on minors. Nor may it be carried out on persons at the request of third parties, such as doctors, insurance companies, adoption agencies or employers.
Treatment Of Huntington´s Disease:
Huntington´s disease is not curable. Nevertheless, certain medications can relieve symptoms. For example, the active ingredients tiapride and tetrabenazine can restrict excessive and uncontrolled movements by counteracting the body’s own messenger substance dopamine. In depressive moods, antidepressants from the group of selective serotonin reuptake inhibitors (SSRI) or sulpiride can reduce the symptoms.
There is no official therapy recommendation against the development of dementia in Huntington’s disease. In some studies, the active substance memantine has been shown to slow down mental deterioration.
In addition to drug therapy for Huntington’s disease, supportive measures such as physiotherapy, occupational therapy, and speech therapy can also help to relieve the symptoms. For example, special exercises can improve speech or swallowing disorders. Occupational therapy can also be used to train the activities of everyday life. This enables people with Huntington’s disease to remain independent for longer. Psychotherapy helps many affected people to cope better with the disease. Self-help groups are also a great support for many people.
Since many people with Huntington’s disease lose a lot of weight during the course of their illness, a high-calorie diet is recommended. In some cases, being slightly overweight improves the symptoms of Huntington’s disease.
Huntington’s disease – Research For Treatments
Therapies that could stop the underlying degradation process in Huntington’s disease are not yet known. A variety of new approaches are being pursued in drug-based Huntington’s disease therapy, but these are still in the experimental stage. High doses of CoEnzyme Q10 have shown slightly positive effects in studies, but overall they do not affect the course of the disease. Coenzyme Q10 is a protein that occurs naturally in the body and protects the cells from damage.
Another active substance for the treatment of Huntington’s chorea is ethylcosapent, a drug especially developed for the treatment of Huntington’s disease, which is produced from the fish oil component eicosapentaenoic acid. Ethylcosapent is designed to prevent damage to certain cell components that play a role in cell death and to increase the performance of diseased nerve cells. This drug was also unable to improve movement disorders.
Prognosis Of Huntington´s disease
Huntington´s disease is not curable. The patients die on average 19 years after the onset of this condition. This is only an average value, which means that individual persons can die much later or earlier from the consequences thereof.
Which symptoms the affected persons develop and how well they respond to the various drugs varies greatly. Only specialists who deal with Huntington´s disease on a daily basis are sufficiently familiar with the many special features of the disease. For this reason, it is recommended that Huntington’s patients have regular check-ups at one of the Huntington’s centers in their country in order to adapt the individual therapy to the current course of the disease.