Huntington’s Disease: Causes, Symptoms, Diagnosis, Treatment, and Prevention
A rare, inherited disease, Huntington's disease (HD) causes nerve cells in the brain to breakdown and die over time. HD affects the brain areas that control movement, thinking, and emotions. Despite the fact that HD cannot be cured, treatments can help manage symptoms and improve the quality of life of people with HD and their families. HD can cause physical, mental, and behavioral problems that worsen over time.
Causes of Huntington’s Disease
An abnormal expansion of a repeated sequence of three DNA letters (CAG) in the gene is responsible for HD, which is caused by a mutation in the huntingtin gene (HTT). In people with HD, the CAG repeat can range from 10 to 35 times. However, it can grow to 36 to 120 times in patients. Symptoms usually appear earlier and are more severe when the CAG repeat is longer.
The mutation in HTT is inherited in an autosomal dominant manner, which means that a person only needs one copy of the mutated gene from either parent to develop HD. About 10% of cases are caused by a new mutation that occurs during the formation of sperm or egg cells. Children of a parent with HD have a 50% chance of inheriting the mutation.
Symptoms of Huntington’s Disease
HD symptoms can vary from person to person and can develop at any age, but they usually begin between 30 and 50 years old. The symptoms can be divided into three categories: movement disorders, cognitive disorders, and psychiatric disorders.
Movement disorders are problems with voluntary and involuntary movements, such as:
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Chorea: involuntary jerking or writhing movements that can affect any part of the body
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Dystonia: muscle stiffness or spasms that can cause abnormal postures or facial expressions
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Bradykinesia: slowness of movement that can affect walking, speaking, or swallowing
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Dyskinesia: abnormal or unwanted movements that can interfere with daily activities
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Gait and balance problems: difficulty with walking, coordination, and maintaining posture
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Eye movement problems: difficulty with tracking objects or shifting gaze
Cognitive disorders are problems with thinking and reasoning abilities, such as:
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Impaired executive function: difficulty with planning, organizing, prioritizing, or multitasking
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Impaired memory: difficulty with learning new information or recalling past events
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Impaired attention: difficulty with focusing, sustaining, or switching attention
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Impaired language: difficulty with finding words, expressing thoughts, or understanding speech
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Impaired visuospatial skills: difficulty with recognizing objects, faces, or shapes
Psychiatric disorders are problems with mood and behavior, such as:
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Depression: persistent feelings of sadness, hopelessness, or guilt that can affect appetite, sleep, energy, or interest in activities
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Anxiety: persistent feelings of nervousness, worry, or fear that can affect breathing, heart rate, sweating, or trembling
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Irritability: increased tendency to get angry, frustrated, or annoyed easily
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Apathy: decreased interest or motivation in activities or people
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Impulsivity: increased tendency to act without thinking or considering consequences
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Obsessive-compulsive disorder (OCD): recurrent and intrusive thoughts or compulsive behaviors that are difficult to control
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Psychosis: loss of contact with reality that can involve hallucinations (seeing or hearing things that are not there) or delusions (false beliefs that are not based on facts)
Diagnosis of Huntington’s Disease
A genetic test can detect the presence and length of the CAG repeat in HTT, which is used to diagnose HD. Regardless of whether symptoms are present or not, genetic testing can be done at any time. However, genetic testing has ethical implications, which should be discussed carefully before proceeding.
Genetic testing can confirm HD in people with symptoms or a family history. It also can predict HD in people who don't have symptoms but are at risk due to a parent's HD. This is called predictive testing. Predictive testing can help people make decisions about their future plans and health care options. Predictive testing cannot, however, predict when or how severe symptoms will occur.
Prenatal testing can also be performed to determine if the fetus has inherited the mutation from an affected parent. Prenatal testing can be used to help parents decide whether to continue or terminate a pregnancy. However, prenatal testing does have ethical implications and should only be performed after thorough counseling and informed consent has been given.
Treatment of Huntington’s Disease
The progression of HD cannot be stopped or reversed, but there are treatments that can help manage some of the symptoms and improve quality of life for people with HD and their families.
Movement, cognitive, and psychiatric symptoms of HD can be reduced by medications. Tetrabenazine, for instance, can reduce chorea, antidepressants and antipsychotics can treat depression and anxiety, mood stabilizers can treat impulsivity and mood swings, and antipsychotics can treat psychosis and irritability. A doctor needs to monitor medications for side effects and interactions as well.
The symptoms of HD can also be managed and maintained through non-medical treatments. Strength, balance, and mobility can be improved by physical therapy, daily activities and assistive devices can be assisted by occupational therapy, communication and swallowing can be improved by speech therapy, memory and problem-solving can be improved by cognitive therapy, and stress management and coping skills can be improved by behavioral therapy. Furthermore, family, friends, and support groups can provide emotional and practical support.
Prevention of Huntington’s Disease
There is no way to prevent HD since it is caused by an inherited or random mutation. However, people at risk of HD or who have HD can take steps to reduce the disease's impact on their health and well-being.
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Seek genetic counseling and testing to learn about their risk and options
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Seek medical care and follow-up to manage their symptoms and monitor their condition
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Seek non-medical care and support to cope with their challenges and needs
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Maintain a healthy lifestyle that includes regular exercise, balanced diet, adequate sleep, and avoiding smoking, alcohol, and drugs
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Participate in activities that they enjoy and that stimulate their mind and body
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Plan for their future needs and wishes regarding their health care, finances, legal matters, and end-of-life care
There is no cure for Huntington's disease, but treatment can help manage some of the symptoms and improve the quality of life for people with HD and their families. It affects the brain and causes physical, mental, and behavioral problems that worsen over time. In order to understand their risks and options for HD, people who have it or are at risk should seek genetic counseling and testing. In addition to seeking medical care and support, they should maintain a healthy lifestyle and make plans for their future needs and wishes. By doing so, they will be able to live as comfortably as possible with HD.
