The Huntington ‘s disease is a fatal genetic disorder that causes progressive breakdown of nerve cells in the brain, has a broad impact on the functional capabilities of a person and usually results in disorders of movement, thinking (cognitive) and psychiatric.
Most people develop signs and symptoms in their 30s or 40s, but the disease can appear earlier or later in life. When the disease develops before the age of 20, the condition is called Juvenile Huntington’s disease, an earlier onset of the disease often results in a somewhat different set of symptoms and with a much more rapid progression of the disease.
Medications are available to help control symptoms, but treatments cannot prevent the physical, mental, and behavioral decline associated with the disease. It is known as the quintessential family disease because each child of a parent with this disease has a 50/50 chance of carrying the defective gene.
Huntington’s disease history
In 1872, George Huntington described the disorder in his first article at the age of 22, although it has been recognized as a disorder since at least the Middle Ages, the cause has been unknown until relatively recently. Huntington was given different names throughout this story as understanding of the disease changed. Originally simply called ‘chorea’ for the uneven dance movements associated with the disease, it has also been referred to as ‘hereditary chorea’ and ‘chronic progressive chorea’.
The first mention was due to a letter by Charles Oscar Waters, published in 1842, where he described “a form of chorea, commonly called lean,” which includes precise descriptions of chorea, its progression, and the strong inheritance of the disease. In 1846, Charles Gorman observed how the highest prevalence seemed to occur in localized regions, independently of Gorman and Waters, both Dunglison students at Jefferson Medical College in Philadelphia, and Johan Christian Lund also produced an early description in 1860, specifically noting that in Setesdalen, In an isolated mountain valley in Norway, there was a high prevalence of dementia associated with a pattern of sudden movement disorders that ran in families.
The first comprehensive description of the disease was made by George Huntington in 1872, when examining the combined medical history of several generations of a family with similar symptoms, he realized that their conditions must be related; presented his detailed and precise definition of the disease as his first article. Huntington described the exact pattern of inheritance for autosomal dominant disease, years before scientists’ rediscovery of Mendelian inheritance.
William Osler was interested in the disorder, and was impressed with Huntington’s work, stating that “In the history of medicine, there are few cases in which a disease has been described more precisely, more graphically, or briefly.” Osler’s continued interest, combined with his influence in the medical field, helped rapidly spread awareness and knowledge of the disorder throughout the medical community.
Causes of Huntington’s disease
Huntington’s disease is caused by a faulty gene that runs in families.
Genes and chromosomes
Genes are the instructions for all parts of the human body and brain, they are made of DNA and packaged in strands called chromosomes, we have two copies of all our genes, so our chromosomes are in pairs. Humans have 46 chromosomes (23 pairs). The faulty gene that causes Huntington’s disease is located on chromosome number four.
The normal copy of the gene produces a protein called huntingtin, but the defective gene contains an abnormal region, this area is larger than normal and produces a mutant form of huntingtin. Cells in parts of the brain, specifically the basal ganglia and parts of the cortex, are very sensitive to the effects of abnormal huntingtin, this causes them to malfunction and they eventually die.
The brain normally sends messages through the basal ganglia and cortex to control movement and thinking as well as motivation , if this part of the brain is damaged it causes problems with control of movement, behavior and thinking.
It is not yet clear exactly how abnormal huntingtin affects brain cells and why some are more sensitive than others.
Huntington’s disease symptoms
The clinical features of the disease can include psychiatric problems and difficulties with behavior, eating, communication, and abnormal movements. People can begin to show the characteristics of Huntington’s disease at almost any age, but most will develop problems between the ages of 35 and 55.
The condition usually progresses and worsens for about 10-25 years, until the person finally dies. Signs and symptoms can vary between individuals and there is no typical pattern.
Initial characteristics, such as personality changes, mood swings, and unusual behavior, are often overlooked at first and attributed to something else. Some people with Huntington’s disease may not recognize that they have a problem.
Changes in behavior are often the first features to appear in the disease and can be the most distressing. These changes often include:
- A lack of emotions and not recognizing the needs of others in the family.
- Alternating periods of aggression, excitement, depression, apathy, asocial behavior, and anger
- Difficulty concentrating on more than one task and handling complex situations
- Irritability and impulsiveness
A person with Huntington’s disease may lack drive, initiative, and focus, making them appear lazy. However, this is not the case, it is just the way the condition affects the brain. As part of this, they may also develop a lack of interest in hygiene and personal care.
Many people with Huntington’s disease have depression. This occurs as part of the condition, not just as a response to the diagnosis. Symptoms of depression include continued low mood, low self-esteem, lack of motivation or interest in things, and feelings of hopelessness.
Some people can also develop obsessive behaviors and schizophrenic-type problems, although this is relatively rare.
Studies have shown that people with Huntington’s disease are more likely to consider suicide , particularly around the time of diagnosis when the condition becomes apparent, and when they begin to lose their independence.
Huntington’s disease affects movement. Early features include slow and uncontrollable movements of the face and jerking, or restless movements of the limbs and body. These move from one area of the body to another and can cause the person to wobble and wobble.
These features are often first seen when the person is walking or resting (sitting in a chair or lying in bed).
As the condition progresses, the uncontrollable movements will become more frequent and extreme. However, over time this can change and in the advanced stages of the condition a person’s movements may become slow and their muscles stiffer.
People with this disease tend to lose weight, despite having a good appetite, they may find eating tiring, frustrating, and messy because the muscles of the mouth and throat are not working properly due to loss of motor control. In some cases, this can lead to choking and recurrent chest infections.
Loss of coordination can lead to food spills or falls. Swallowing is a problem, so choking on food and drink, especially thin drinks like water, can be a common problem. A referral to a dietitian or speech and language therapist may be necessary if there are swallowing difficulties, in some cases a feeding tube may be inserted.
Communication and cognition ( perception , awareness, thinking, and judgment) are affected by Huntington’s disease. People with this condition often have difficulty expressing their thoughts in words and speaking badly, they can understand what is being said, but they may not be able to respond or communicate what they understand. However, over time, a person with the disease will become less receptive, more withdrawn, and communicate little.
Huntington’s disease complications
After the onset of the disease, functional abilities gradually worsen over time, the rate of progress and duration varies, the time from onset to death is usually 10 to 30 years. Juvenile Huntington’s disease usually causes death within 10 years after symptoms appear.
The clinical depression associated with the disease can increase the risk of suicide, some research suggests that the increased risk of suicide occurs before a diagnosis is made and intermediate stages of the disease when a person has begun to lose independence.
Finally, a person requires help with all activities of daily living and attention. At the end of the illness, he or she is likely to be confined to a bed and unable to speak, however, he or she can generally understand language and has an awareness of family and friends.
Common causes of death include:
- Pneumonia or other infections.
- Injuries related to falls.
- Complications related to the inability to swallow.
Huntington’s disease treatment
There is no cure for Huntington’s disease, its progress cannot be reversed or slowed down, although this is the goal of many research projects. Some of the characteristics can be managed with medications and therapies, which can be coordinated by specialized teams.
Therapies, such as speech and language therapy and occupational therapy, can help with communication and everyday life. Regular exercise is also very important. People who are active tend to feel much better physically and mentally than those who do not exercise, a person with Huntington’s disease may have poor coordination, but walking independently, with the use of walking aids if necessary, can Make a Difference.
Medicines for Huntington’s disease can be taken in liquid form in many cases, if necessary. Most of these have side effects, such as extreme tiredness, however it can sometimes be difficult to determine if these are symptoms of the condition or a result of the medication.
Antidepressants to treat depression
Antidepressants can help improve mood swings and treat depression. They include:
- SSRI antidepressants, such as fluoxetine, citalopram and paroxetine.
- Tricyclic antidepressants, such as amitriptyline.
- Other types of antidepressants, including mirtazapine, duloxetine, and venlafaxine
Side effects include:
- Difficulty sleeping ( insomnia )
Mood stabilizers to treat irritability or mood swings
Mood stabilizers, particularly carbamazepine, can be considered as a treatment for irritability. Olanzapine can also help, along with sodium valproate and lamotrigine. The dose of carbamazepine should be increased slowly and any side effects monitored, it cannot be used during pregnancy.
Medication to suppress involuntary movements
The medications listed below suppress the involuntary movements, or chorea, seen in Huntington’s disease. In the UK, antipsychotic drugs are generally preferred.
- Antipsychotic medication, such as olanzapine, sulpiride, risperidone, and quetiapine
- Tetrabenazine: reduces the amount of dopamine that reaches some of the nerve cells in the brain
- Benzodiazepines, such as clonazepam and diazepam
Antipsychotic medication can also help control delusions and violent outbursts, however they can have serious side effects, such as:
- Slow movements
Huntington’s disease diagnosis
It can be done after the appearance of specific physical symptoms of the disease. Genetic testing can be used to confirm a physical diagnosis if there is no family history.
Cross section of a brain showing undulating tissues with spaces between them, there are two large spaces evenly spaced around the center.
Coronal section of a patient’s MRI brain scan, showing atrophy of the heads of the caudate nuclei, enlargement of the frontal horns of the lateral ventricles, and generalized cortical atrophy
A physical exam, sometimes combined with a psychological exam, can determine if the onset of the disease has begun.
Predictive genetic testing
Because it follows an autosomal dominant inheritance pattern, there is strong motivation for people who are at risk of inheriting it to seek a diagnosis. The genetic test consists of a blood test that counts the number of repetitions in each of the alleles.
Preimplantation genetic diagnosis
Embryos produced using fertilization can be genetically evaluated using preimplantation genetic diagnosis. This technique, where one or two cells are removed from a typically 4-8 cell embryo and then tested for the genetic abnormality, can be used to ensure that affected embryos do not implant, and therefore any offspring will not inherit the disease. .
It is also possible to obtain a prenatal diagnosis for an embryo or fetus in the uterus, using fetal genetic material acquired through chorionic villus sampling, an amniocentesis can be performed if the pregnancy is more advanced, within 14-18 weeks. This procedure tests the amniotic fluid around the baby for indicators of the mutation.
Huntington’s disease prevention
People with a known family history of Huntington’s disease are understandably concerned about whether they can pass the Huntington gene to their children, these people may consider genetic testing and family planning options.
If an at-risk parent is considering genetic testing, meeting with a genetic counselor may be helpful. A genetic counselor will discuss the potential risks of a positive test result, which would indicate that the father will develop the disease, in addition, couples will need to make additional decisions about whether to have children or consider alternatives, such as prenatal testing for the gene or the fertilization with donor sperm.
Another option for couples is fertilization and genetic diagnosis prior to implantation. In this process, the eggs are removed from the ovaries and fertilized with the father’s sperm in a laboratory, the embryos are analyzed for the presence of the Huntington gene, and only those that test negative for the gene are implanted in the mother’s uterus.
Hello, how are you? My name is Georgia Tarrant, and I am a clinical psychologist. In everyday life, professional obligations seem to predominate over our personal life. It's as if work takes up more and more of the time we'd love to devote to our love life, our family, or even a moment of leisure.