In the case of Huntington’s chorea, the genetic mutation that causes it is a repeat of CAG nucleotides in the huntingtin gene.
Nucleotides are the building blocks of DNA. Its repetitions and variations define what will be produced by the body.
In people without the disease, the number of CAG repeats in this gene is between 10 and 26, which is normal and necessary. In people with Huntington’s disease, there are more than 39 repetitions, which can reach 120 or more.
It is possible to develop the condition when the repetitions are between 27 and 38, but only after 39 you can be sure. People with 38 repetitions may never have Huntington’s, while people with 27 may have the disease.
Where does it affect?
It is not known how the defective protein causes damage to neurons, but it is known that the disease is capable of degenerating the lenticular nuclei , part of the basal ganglia . The main functions of this region are to perform coarse movements (broad, such as steps) and influence different types of learning. The result is Huntington’s chorea.
Huntington’s Korea is an autosomal dominant genetic disorder .
A little bit of genetics
Humans have 23 pairs of chromosomes, one of which defines the person’s biological sex. The other 22 pairs are called autosomes and will define body characteristics such as height, eye color, hair and everything else.
The sperm carries half of the genetic load of man. That is, it does not take the 23 pairs, but only 23 chromosomes alone. The egg does the same, taking 23 chromosomes from the woman. When they come together to create the baby that will be born, genetics are formed in pairs of the child with the sum of the parents’ chromosomes.
Huntington’s disease is caused by a genetic change in any of the autosomal pairs of chromosome 4 (in the gene called huntingtin ).
When it is recessive, it is necessary for both chromosomes of the affected pair to be altered, but in case it is dominant, it is enough that one of them is so for the disease to manifest, as it is in the case of Huntington’s disease.
For a recessive disease to manifest, the two chromosomes in the pair must have the change. If only one of them is changed, the disease does not appear.
Imagine that both parents of a child have only one of the chromosomes altered.
- Mother: Altered 1 – Normal 1;
- Parent: Normal 2 – Changed 2.
Neither of them has the disease, but they can pass it on to their children. Of these chromosomes, only one of each will go to the child. It has four possible combinations:
- Normal 1 – Normal 2;
- Normal 2 – Altered 2;
- Altered 1 – Normal 1;
- Changed 1 – Changed 2.
In the first combination, there is no altered gene and that person cannot pass the disease forward, nor will it manifest it. In the two combinations of the environment, the child is like his parents: he does not manifest the disease, but he has the possibility of passing it on to his children.
The fourth combination is a child who manifests the disease. If that child has children, they will all carry at least one of the altered genes.
If only one parent has the altered gene, none of the children will manifest the disease as they will have, at most, only one altered gene.
When the disease has a dominant characteristic , it is enough that one of the chromosomes in the pair is altered for it to manifest. Let’s show it again:
- Mother: Normal 1 – Normal 2;
- Parent: Normal 1 – Changed 2.
In this case, only the father has the altered gene. But as Huntington’s disease is a dominant characteristic, it manifests it. The son of this couple has 4 possibilities:
- Normal 1 – Normal 1;
- Normal 1 – Altered 2;
- Normal 2 – Normal 1;
- Normal 2 – Changed 2.
The difference here is that just one altered gene is enough for the disease to appear. The first and third combinations do not have the disease nor are they able to pass it on to the next generation, but the second and fourth combinations manifest the condition and transmit it.
Group of risk
There is a possibility that the genetic mutation will happen spontaneously and the person will be born with the disease even if neither parent has it, but this is extremely rare. As a rule, in the risk group, there are children of patients with Huntington’s disease.
As the disease is dominant , if a parent has the altered gene, there is a 50% chance that the patient will inherit this gene.
The symptoms of Huntington’s disease usually manifest only in adulthood and are diverse. They evolve gradually, becoming more pronounced over time, and can be divided into physical , cognitive and emotional and personality .
Physical symptoms are the first to be noticeable. They involve motor skills and are the first sign that something is wrong .
Chorea is the most pronounced symptom of the disease and gives one of its names. Damage to the nervous system causes involuntary movements and rapid, irregular spasms. They have no purpose and are usually present on the patient’s face and limbs.
A small number of patients of Huntington’s disease do not exhibit chorea, so the original name of the disease ( chorea Huntington’s) began to be replaced.
This symptom is usually one of the initial symptoms. It starts with small involuntary spasms in the fingers and face and, over the years, evolves. The person starts to feel a little more clumsy and the situation gets worse with time.
Bradykinesia is the slow movement. Over time it affects the whole body. Voluntary movements become noticeably slow, slowing down daily activities such as eating, dressing or bathing.
The disease can cause muscle stiffness, making movement more difficult.
The dysarthria is a neurological symptom that causes difficulty of muscular movements of the mouth and connected speech, difficult chewing, swallowing, movement of facial muscles and difficulty in speech articulation.
Loss of peripheral vision
Peripheral vision can gradually be lost by the patient.
Cognition involves activities such as memory, speech, focus and planning. These symptoms take longer to become noticeable , but over time they start to appear.
It is important to note that although Huntington’s disease affects memory and planning, the patient recognizes people and knows where they are and what day they are on, for example. The person is not disoriented at any time of the disease.
Progressive memory loss is one of the symptoms of Huntington’s disease. The patient loses his memory over time, forgetting events that he would remember being healthy.
In addition to dysarthria, speech problems can arise. Disorganized, explosive, incomprehensible, or hesitant speech may be present in a Huntington’s disease patient.
Planning a time or following a recipe can become more difficult for the person with Huntington, especially with the progression of the disease.
Emotional and personality
These symptoms involve changes in behavior and emotion, sometimes inappropriate to the person’s situation.
Huntington’s disease patients may experience depression , anxiety , irritability, hypersexuality, self-centeredness and other disorders.
Common in the early stages of the disease, the person may feel more irritated, sometimes without knowing what with.
Approximately one third of patients have depression, which can and should be treated.
Inappropriate emotional responses
People with Huntington’s can smile or laugh in inappropriate situations or cry for no apparent reason.
The way to react to certain situations can change in patients with Huntington’s disease. It is important to remember that this is a symptom of the disease and is not anyone’s fault.
Other psychiatric disorders
Anxiety, hypersexuality and bad mood are some of the other symptoms that can arise in the patient. They are varied and progressive.
In approximately 8% of cases the disease manifests itself in people under the age of 20. The symptoms are no different, however in the case of juvenile Huntington’s disease, chorea is less pronounced and bradykinesia is more evident.
In these cases, the disease usually progresses more quickly. Its initial symptoms are major changes in behavior and school performance, in addition to learning problems.
How is the diagnosis made?
The diagnosis of the disease is made through genetic and imaging tests, in addition to neurological tests and neuropsychological assessments.
Computed tomography (CT) and magnetic resonance imaging (MRI) are tests used to find physical changes that can be caused by Huntington’s disease in the patient’s brain. In the early stages, changes may not appear on these tests, as the disease progresses by degenerating parts of the brain over time.
The neurologist can perform tests that seek to assess neurological status, motor functions, reflexes, muscle tone, balance and senses.
The neuropsychologist is responsible for the neuropsychological assessment . It serves to assess memory, reasoning, mental alertness, cognition, language functions and learning functions.
The psychiatrist performs tests to assess mood, behavior, judgment and other areas.
This method is able to identify Huntington’s disease at any point in a person’s life. It is usually only done on patients after they have symptoms, as the disease is rare and the test can be costly – both in resources and time.
He is able to confirm whether there is a change in the huntingtin gene. The test can be done on people whose parents or relatives have the disease to find out if it will manifest itself as well.
There are several diseases that can be caused by genetic problems. To perform the exam, a blood or saliva sample is required. [
In the case of Huntington’s chorea the genetic mutation that causes it is a repetition of CAG nucleotides in the huntingtin gene and the genetic examination counts this repetition.
On average, the CAG sequence reaches 17 repetitions. In people without the disease, repetitions are between 10 and 26. However, in people with the disorder, there are more repetitions.
To find out if Huntington’s disease is certain to occur, there must be more than 39 repetitions. They can reach up to 120 or more.
The gray zone
When CAG repetitions are between 27 and 39 the situation gets more complicated. This is called the gray zone .
People with repetitions between 27 and 35 do not develop Huntington’s disease, but their descendants can do so.
People with repetitions between 36 and 39 are in the interval called “reduced penetrance”. Some of these people will develop the symptoms of Huntington’s chorea and some will not, but it is impossible to be sure which groups will do it.
Should I do genetic mapping?
Although it is possible to diagnose the disease before it manifests itself, even as a child, many people prefer not to do so.
Even with the diagnosis in hand, there is nothing you can do with it. The disease cannot be prevented. So knowing that it will come can be an anguish for some people. Taking the test goes from person to person.
Is there a cure?
Huntington’s disease has no cure . The treatment that exists is for the relief of symptoms and palliative, but unfortunately it is not possible to eliminate the disease, only to improve the quality of life of the patient.
What is the treatment?
The treatments available for Huntington’s disease aim to reduce the negative effect of symptoms on patients’ lives and unfortunately cannot cure the disease. They are as follows:
Physical therapy can help the patient maintain muscle strength and tone, reducing symptoms of chorea.
Psychological treatment may be necessary for both the patient and the people around him. The disease, which has no prospect of cure and causes progressive degeneration, can lead to depression and psychological support is very important for the patient’s quality of life.
Medicines can be used to control symptoms, especially psychiatric and motor disorders. Antidepressants, antipsychotics, drugs for chorea, among others, can be used for symptoms.
Some of the drugs used for the symptomatic treatment of Huntington’s disease are:
- Thiamine hydrochloride ( Neurivit )
- Carbidopa + Levodopa ( Carbidol )
NEVER self-medicate or stop using a medication without first consulting a doctor. Only he will be able to tell which medication, dosage and duration of treatment is the most suitable for his specific case. The information contained in this website is only intended to inform, not in any way intended to replace the guidance of a specialist or serve as a recommendation for any type of treatment. Always follow the instructions on the package insert and, if symptoms persist, seek medical or pharmaceutical advice.
Living with Huntington, as with any degenerative disease, is a challenge and a constant struggle. Both the patient and those around him may need help. Check out some tips for coexistence:
Although there is no cure, the diagnosis of Huntington’s disease does not mean that life is over. There are many ways to maintain quality of life and continue to enjoy it as much as possible
It is important that you carry out the disease monitoring and treatment to the letter! It is these two habits that guarantee a higher quality of life in the years that follow the diagnosis.
Keep friends close. This is very important, as support during the illness is necessary and should be welcomed. You can also look for disease support groups to help you deal with it better.
Psychological counseling is of the utmost importance. The diagnosis of a disease like Huntington’s can cause psychological problems, which a psychologist can help deal with. Some of the symptoms, such as depression, can also be relieved through therapy.
Exercises and physiotherapy
Through exercise and physical therapy you can maintain physical control for longer. These practices slow down motor problems. The sooner they start, the better.
Therefore, patients who have a genetic diagnosis before they start to develop symptoms can begin to prepare years earlier for a smoother progression of the disease.
Keep your mind active
Exercising the brain can delay the neurological effects of the disease. It is a way to delay her progress and improve the patient’s quality of life. As with exercise, if there are frequent mental exercises during life before the disease manifests, its progression may be smoother.
You can exercise your brain through games like crosswords, sudoku, chess, playing musical instruments, as well as being able to learn new things to train different parts of the brain. Learning how to play an instrument or a new sport is a good way to do that.
For people close to you
The Huntington’s disease patient, over time, may begin to exhibit behaviors that people close to him may have difficulty dealing with.
If someone close to you has the disease, remember that it is one of their symptoms and that you can get help too.
The psychological monitoring of those close to the patient is also important. Although the burden of dealing with the disease is heavier for the patient, it is a difficult task for everyone involved and taking care of the psychological is indispensable. The recommendation also goes to those who can inherit the disease.
Unfortunately, the prognosis for Huntington’s disease is not good. Symptoms usually appear between the ages of 30 and 50 and from then on they only get worse. Treatments can improve the patient’s quality of life and slow down degeneration, but are unable to stop it.
After the first symptoms appear they gradually worsen over the years until the patient’s death, which usually happens after 15 to 20 years.
In December 2017 the Huntington’s Disease Center at the University College of London announced results of a new drug being tested in humans. 46 patients diagnosed with initial Huntington’s disease received the drug and the test results were encouraging, indicating slowing down and even stabilizing the progression of the disease.
The drug works by reducing the amount of the huntingtin protein in the brain. Still in the testing phase, there is no confirmation that it works effectively, since only 46 people were in the study, but the news is encouraging for people with the condition.
Over the years, the disease becomes more intense and pronounced, causing complications resulting from the symptoms that are accentuated. Are they:
The patient becomes dependent over time. Neurological degenerations start to cause mobility and neurological problems and the patient may need help with basic tasks such as eating or using the bathroom.
Due to involuntary movements, falling is a risk for the patient. When the patient is older this can be even more dangerous due to the fragility of the body.
Depression and anxiety
The prospect of a life with a degenerative disease can cause psychological illnesses such as depression and anxiety. Suicide is common among patients with the diagnosis due to the present impossibility of curing the disease.
Huntington’s disease always culminates in the death of the patient as a result of the symptoms. The difficulty in swallowing can cause malnutrition in addition to choking. Frequent falls due to chorea can injure the patient and other symptoms can lead to death such as cardiac arrest or infections.
How to prevent
There is no way to prevent genetic diseases. It is possible to perform genetic mapping to find out if the disease is present in your genes, but if it is, it is likely that a relative will present it throughout life.
Genetic counseling is an option. If the altered gene is present in any part of the couple who wish to have children, the geneticist can advise and explain possible paths and options.
Artificial insemination – preimplantation genetic diagnosis
Artificial insemination is a method that can be recommended by the geneticist. It is not possible to prevent the disease itself, but you can prevent it from spreading.
Through pre-implantation genetic diagnosis it is possible to know if a specific sperm or egg has the altered gene. Thus, the patient who has Huntington’s can avoid using the gamete (sperm and eggs) that has the disease.
Huntington’s disease is a serious, rare, serious genetic condition that brings suffering to the patient and those close to him. Unfortunately it has no cure. Share this text with your friends to raise awareness about this sad illness.