Huntington’s chorea . Degenerative neurological disease (affects certain areas of the brain where neurons degenerate and eventually die) characterized by:
- Uncontrolled involuntary movements.
- Psychic disorders.
- Loss of intellectual functions (dementia)
Specifically, the affected cells are those of the basal ganglion, a deep structure of the brain that has important functions, including the coordination of movements. In the basal ganglion, Huntington’s Disease specifically attacks striatal neurons, especially the caudate and pallid nuclei. Another part of the brain is affected, which is the cortex, which controls thought, perception and memory. The disease is named because it was described by George Huntington in 1872, also known as Korea (from the Greek dance) for the characteristic movement of affected people. For a long time it has been known as “Baile de San Vito”.
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- 1 Causes
- 1 Inheritance
- 2 Epidemiology
- 3 Symptoms
- 4 Diagnosis
- 5 Forecast
- 6 Treatment
- 7 Rehabilitation
- 8 Source
It is an inherited, autosomal and dominant disease, so each child of a father or mother with the disease has a 50% probability of inheriting it. If the son does not inherit the gene that causes the disease, he will not have it and will not pass it on to his offspring.
A person’s appearance and mental abilities and talent are conditioned by genes, by inheritance. Some diseases, or the susceptibility to it, are determined by genes. Genes are the smallest units of inheritance. The gene is a small segment of DNA that is interpreted by the body as a pattern for the production of a specific protein and the information provided by all of them is the design to structure the human body and its functions. Genes are arranged in order along the DNA chain on the chromosome within the nucleus of cells. In the nucleus of each cell there are 23 pairs of chromosomes, two of these chromosomes are called X and Y and they are the sex chromosomes and determine the sex; the rest are called autosomal. Each gene is made up of a chain of molecules called nucleotides that are adenine (A), cytosine (C), guanine (G), and thymine (T). The gene is made up of a series of three nucleotides (trinucleotide). Genetic diseases are called recessive and dominant. Dominant genetic traits are those that occur when one gene in the gene pair can control the trait for which that pair of genes encodes, and recessive traits require both genes in the pair to work together to control the trait. Each parent contributes half of each pair of chromosomes to the baby; women contribute an x chromosome and the father contributes one X (female) or one Y (male), so it is the one that determines the sex. Some of the DNA is found in the mitochondria of cells, which have important genes in their own DNA strand, what is called the mitochondrial chromosome. All of the child’s mitochondrial chromosomes come from the mother: maternal inheritance. An inherited abnormal trait can:
- Not have real consequences on the health and well-being of the person.
- Minimal consequences.
- Produce effects that produce a significant decrease in quality or life expectancy.
If a gene is abnormal it can produce an abnormal protein or an abnormal amount. Because the autosomal chromosomes are in pairs, there are two copies of each gene, and if one is defective, the other can code to produce enough protein, and the abnormality is not clinically visible. This case is known as a recessive disease and the gene is said to be inherited in a recessive pattern. If an abnormal gene causes the disease, it is called a dominant inherited disorder. There are five basic single gene inheritance patterns:
- Autosomal dominant.
- Autosomal recessive.
- Dominant X-linked
- X-linked recessive.
- Maternal (mitochondrial) inheritance.
In autosomal dominant inheritance, abnormalities generally appear in each generation, and each affected child has an equally affected parent, and each affected parent child has a 50% chance of inheriting the disease. Normal members do not transmit the disease, and men and women are equally likely to have the disease and to transmit it. It has been known for some time that the genetic abnormality resided on chromosome 4 and in 1993 the portion of the gene responsible (expansion of CAG triplets in the IT15 gene on chromosome 4) was discovered, in such a way that people of risk before disease begins. In the normal population there are up to 34 repetitions of the CAG trinucleotide (cytosine-adenosine-guanine) in this portion of the gene and in Huntington’s disease there are more than 40.
The age of onset is between 30 and 45 years, although it can occur from two years. Children who develop the disease rarely reach adulthood. The prevalence of Huntington’s disease (HD) is considered between 5 and 10 cases per 100,000 inhabitants, somewhat lower in East Asian countries and in the black population. The annual incidence varies between 1 and 4 cases per million inhabitants. Genealogical studies have allowed us to locate the origin of the disease in western Europe ( France , Germany and the Netherlands), being the emigration of these families, probably in relation to the dispersal of the Huguenots to America, England, South Africa and Australia, the origin of the spread of the disease. It is possible that in the future the possibility of carrying out genetic counseling to affected subjects will allow us to see their eradication, at least in developed countries. It affects females and males in the same way.
In this disease, generalizations are not valid, as each case is different from another, although there are some characteristics that are generally met:
- Starting age between 30 and 50 years.
- The first symptoms can be reflected in the form of physical, intellectual or emotional deterioration. Physical symptoms may initially consist of certain nervous activity translated by movement or tics or excessive agitation. These initial symptoms progressively become more marked involuntary movements, with spasms and jerks of the head, neck and extremities, with great difficulty in walking, speaking or swallowing. All of these symptoms can vary greatly from patient to patient.
- Decreased recent memory and difficulty dealing effectively with new tasks.
- Emotional symptoms: there may be periods of depression, apathy, tiredness, irritability, or impulsivity
As we have commented, there will be people with profound mental difficulties and others with very few, such as involuntary movements, where there may be patients who practically do not have them. In the majority of patients, ocular changes usually occur, with difficulties in fixation. Generally, the first thing that appears are subtle changes in personality or emotional stability, with irritability, aggressiveness, bad character, inappropriate sexual or social behavior, etc. Mood disorders are frequent, with all the characteristics of manic-depressive illness. Psychiatric illnesses (generally affective disorders) affect approximately 50% of the patients, and suicidal thoughts are frequent. Early cognitive disorders usually consist of a decrease in verbal fluency and memory difficulties that evolve to general dementia. Progressive intellectual decline follows the pattern of all types of dementia, with agnosia (loss of the ability to transform simple sensations into perceptions themselves, therefore not recognizing people or objects) and apraxia (loss of understanding of use of ordinary objects, so it gives rise to absurd acts).
Once the disease is fully developed, the diagnosis is very simple. The main difficulty lies in those patients who have no family history, but in whom progressive chorea, emotional disorders and the onset of dementia in adulthood are typical. The discovery of the HD gene in 1993 made it possible to carry out a test to confirm the diagnosis of the disease in an individual who exhibited symptoms. Using a blood sample, the genetic test analyzes the DNA of the HD mutation, counting the number of repetitions. When there is no family history, the diagnosis can be long delayed. Genetic testing is not diagnostic in itself, even when doctors suspect the disease, they may be reluctant to do it, Because it is such a severe disease with a total change in the person’s life and without solution at the present time. In the case of a family history, you can try to identify if you are a carrier of the defective gene and will develop the disease, but it is not possible to know when or to what degree.
The disease progresses for 15 to 20 years, in which there is an increase in the loss of abilities, requiring full support for any daily activity. Finally, death occurs not from the disease itself, but from complications such as pneumonia, heart failure or infection due to the weak state of the body.
There is currently no specific treatment to cure the disease and the medication used is to help alleviate certain symptoms such as movements, depression, apathy, irritability, etc. Apathy, cessation of any activity, social withdrawal, changes in appetite and weight, fluctuations in mood, are all components of a depressed state. Depression can be caused by a reaction to an external event (death of a family member or the knowledge of having a serious illness) or an endogenous cause. Depression occurs with great frequency in the disease, sometimes as an initial symptom and sometimes in later stages. Depression can be treated in many ways, with changes in our behavior towards them, psychotherapy and medication. Depression in these patients is considered to be treated aggressively. They can experience hallucinations ranging from benign anomalous perceptions of reality to horrifying experiences with no real basis. They can hear special voices, visions, olfactory, tactile or taste experiences. Treating these types of problems can be as simple as having the caregiver explain that what they are feeling is not real. Medication may be necessary to alleviate or control the most severe behavioral disorders. Everything we know about huntingtin today has been discovered in the last 10 years, thanks to the impetus that the Human Genome Project has provided for molecular genetic studies. But this knowledge had not been translated into any results applicable to a possible therapy until recently.
The neurological rehabilitation team works with the patient and his family. The team contributes to setting short and long term recovery goals. The objectives of a neurological rehabilitation program are to help the patient regain the maximum possible level of functionality and independence and to improve their general quality of life, both physically and psychologically and socially. A typical neurological rehabilitation program helps:
- Help with everyday activities like eating, dressing, bathing, going to the bathroom, handwriting, cooking, and basic household chores.
- Language therapy: helping you express your ideas, your way of speaking, diction and communication.
- Counseling (to combat anxiety and depression).
- Activities to improve the control and balance of the muscles of the trunk, pelvis and shoulder girdle.
- An exercise program to improve the functionality, safety, and effectiveness of movements, to prevent or postpone weakness caused by lack of use, to control spasms and pain, to maintain range of motion, and to develop to the maximum the potential capacities of muscles, bones and breathing.
- Social rehabilitation.
- Rehabilitation of gait and balance.
- Nutritional advice.
- Participation in community support groups.
- Activities to improve cognitive problems, such as difficulties with concentration, attention, memory and judgment.
- Education regarding the disease and its process.
- Setting goals (short and long term) with the participation of the patient and his family.
Vocational rehabilitation does not usually give satisfactory results due to the difficulty of learning new tasks.