Huntington Disease (HD)
Huntington Disease (HD) is an autosomal dominant condition that adversely affects the brain, causing irreversible brain impairment and loss of brain function.
What are the other Names for this Condition? (Also known as/Synonyms)
- Huntington Chorea (HC)
- Late Onset Huntington Disease
- Westphal Variant Huntington Disease
What is Huntington Disease? (Definition/Background Information)
- Huntington Disease (HD) is an autosomal dominant condition that adversely affects the brain, causing irreversible brain impairment and loss of brain function. This leads to degeneration of mental and emotional features, and is sometimes accompanied by sudden and involuntarily flailing, limbs and body
- Chief Huntington Disease variants are based on the period of onset: Juvenile Onset HD developing before age 20, and Late Onset HD presenting symptoms after age 30 years
- In all cases, progressive dementia sets in with personality and behavior changes, which may be extremely radical or irrational. Tendencies such as suicide, mania, insanity, and other psychiatric manifestations, are observed
- The condition does not respond to any treatment, and with steady decline of the individual’s health and mental status; the course and outcome of Huntington Disease is often unpredictable
Who gets Huntington Disease? (Age and Sex Distribution)
- Late Onset (also known as Adult Onset) Huntington Disease is the most common type, occurring within the age range of 30-50 years. But, the condition may manifest as late as 80 years, in elderly adults
- Only about 6-10% of the cases are Juvenile HD (presentation age, before 20 years). Infrequently, it has also been noticed in children as young as 2 years
- Both, males and females are equally affected
- West Europeans are more prone to the disorder than Asians or Africans
What are the Risk Factors for Huntington Disease? (Predisposing Factors)
- Huntington Disease runs in the families; hence, individuals born in families with a medical history of the condition are at a serious risk and have a 50% probability of inheriting it
It is important to note that having a risk factor does not mean that one will get the condition. A risk factor increases ones chances of getting a condition compared to an individual without the risk factors. Some risk factors are more important than others.
Also, not having a risk factor does not mean that an individual will not get the condition. It is always important to discuss the effect of risk factors with your healthcare provider.
What are the Causes of Huntington Disease? (Etiology)
- Genetic study and analysis have implicated anomalies in chromosome 4, with abnormal repetition of certain genetic material/sequence, as a primary factor for Huntington Disease
- The repeat sequence of DNA may vary anywhere between 36-120 times in individuals. It has a direct bearing on the early/late onset of the condition and pace of disease progression
- This feature of genetic mutation is normally inherited in an autosomal dominant manner; although in a few cases, spontaneous development of the condition has been noted
Autosomal Dominant: Autosomal dominant conditions are traits or disorders that are present when only one copy of the mutation is inherited on a non-sex chromosome. In these types of conditions, the individual has one normal copy and one mutant copy of the gene. The abnormal gene dominates, masking the effects of the correctly function gene. If an individual has an autosomal dominant condition, the chance of passing the abnormal gene on to their offspring is 50%. Children who do not inherit the abnormal gene will not develop the condition or pass it on to their offspring.
- Juvenile variants of HD progress rapidly, the adult-onset variety progress is slower. However, in both cases, the nerve cells (neurons) lose their function over many years, causing brain shrinkage (termed as cerebral atrophy)
What are the Signs and Symptoms of Huntington Disease?
Huntington Disease presentations affect the physical, mental, and emotional personality. They are diverse and may be initially mild, gradually/rapidly getting more severe, later. These are:
Physical, movement-related signs and symptoms:
- Sudden bursts of involuntary spasms with jerking arms, legs, and body movement (termed as chorea)
- Muscle rigidity, contraction, difficulty walking, maintaining balance, performing basic and routine activities becomes very challenging; loss of basic motor (physical and spatial) skills
- The individual is more prone to accidents and falls
- Speech incoherence, eating/swallowing difficulty, reduced appetite
Mental and emotional quality-related signs and symptoms:
- Progressive deterioration of the senses, memory loss, communication difficulties, unable to plan or organize
- Changes in overall personality; regression or absence of reasoning/rationale, agitation, delusions, depression, aggression, feeling of guilt
- Loss of social abilities, social awkwardness, withdrawal
- Extremely irrational mental/emotional/physical behavior (may be completely inappropriate for the situation); lack of control and awareness, sexual hyperactivity, or absence of sexual drive
- Other extreme behavior include: Suicidal tendencies, mania, bipolar disorder, obsessive-compulsive disorder, impulsiveness, insanity
Children and juveniles may suffer from:
- Academic disorientation, poor performance at regular school activities (both at sports, or exams); gradual memory loss, loss of previously acquired/learned skills
- Behavioral problems, mood swings
- Mild seizures, involuntary physical movements
- Muscle contraction causing stiffness, walking difficulties (affecting gait)
How is Huntington Disease Diagnosed?
To examine for Huntington Disease, a variety of tests are usually conducted. The evaluation is usually based on the set of signs and symptoms present. The main diagnostic tools include:
- Physical exam with a comprehensive evaluation of medical history, including collecting details on any underlying conditions/disorders and their progression
- Neurological and cognitive assessment: Checking intellectual ability, memory, mental health and function, language skills, judgment and reasoning, coordination and balance, reflexes, sensory perceptions (space, sight, hearing, touch)
- Psychiatric examination
- Imaging studies performed are: MRI scan of the central nervous system (brain and spine), CT scan (head), PET imaging of brain
- Blood analysis: Total blood count, blood chemistry, glucose, ammonia, blood gas analysis, electrolytes, vitamin levels
- Urine analysis: Screening for toxic substances, alcohol, determination of vitamin deficiencies
- Cerebrospinal fluid analysis
- Liver and kidney function tests
- Thyroid function tests, such as TSH, T3, and T4
- Electroencephalogram (EEG)
- Genetic study and analysis; particularly when there exists a family history of the condition
Many clinical conditions may have similar signs and symptoms. Your healthcare provider may perform additional tests to rule out other clinical conditions to arrive at a definitive diagnosis.
What are the possible Complications of Huntington Disease?
Complications with Huntington Disease depend on the severity of the condition, age, and overall health of the individual. These include:
- Memory loss and neurological function impairment to a great extent such that institutionalized care might be required for prolonged periods, or for rest of an individual’s life. There is a progressive inability of the individual to take care of themselves, due to complete degeneration of mental and emotional health
- Loss of any inhibition, spontaneous incontinence (involuntary bowel or bladder movement), , prone to fall-related injuries
- Complete loss of personality causing extreme insanity, irrationality, anxiety, delirium, risk of suicide
- The individual may become susceptible to opportunistic infections, heart disease; organ failure chances are higher; due to a reduced sense of hygiene, decreased intake of food/nutrition. Often, these factors lead to an overall reduced lifespan
- Feeding and swallowing problems; food may get blocked in the airways/lungs resulting in pneumonia, choking
- Treatment medication may have significant side effects
How is Huntington Disease Treated?
There is no standard cure or treatment of the condition. Patients receive supportive care and may be given medications to control abnormal spasmodic movements and pain, if any present. Huntington Disease management is undertaken on a case-by-case basis. Some of the methods include:
- Addressing general health problems that are mostly linked to mental balance and well-being. This includes the treatment of anemia, dietary or vitamin deficiencies, heart-related ailments, infections, thyroid disorders, hormonal imbalances, and regulating blood pressure
- Treatment of the underlying illness, to prevent progression of Dementia
- Ensuring that the individual has a nutritious diet with medical supplements (balanced diet that include proteins, fiber-rich fruits and vegetables, milk shakes, juices, and plenty of water)
- Ensuring that the individual is well-cared for in a safe environment (at home, or outside) and is under regular (and maybe constant) care and support
- Use of medications to control involuntary jerky movements (tetrabenazine), and for behavioral issues, to prevent further loss of mental stability; like stimulants, mood stabilizers, dopamine blockers, antipsychotic, antianxiety drugs, sedatives, anti-depressants, etc. Many of these medications may cause side effects like nausea, stomach problems, drowsiness, vomiting, and depression
- Physiotherapy, exercises, to help strengthen the muscles; speech therapy to help muscles in the neck, throat have control of oral activities like chewing, swallowing, and speaking
- Home and work environment can be suitably modified to make it a lot safer and convenient for performing regular activities. This includes safety features normally designed for the physically challenged or the elderly, furniture rearrangement, and use of ramps
- Wheelchairs, walkers, braces are used to provide physical support and promote mobility
- Hospitalization may be required (for short or long duration), depending on the condition of the individual. This is usually followed by regular check-ups
A healthcare provider may utilize the following treatment measures on a case-by-case basis. These are meant to provide mental and emotional support, and develop or retain communication skills:
- Psychiatric treatment
- Group therapy interactive sessions
- Support groups
How can Huntington Disease be Prevented?
- Currently there are no specific methods or guidelines to prevent Huntington Disease genetic condition
- Genetic testing of the expecting parents (and related family members) and prenatal diagnosis (molecular testing of the fetus during pregnancy) may help in understanding the risks better during pregnancy
- If there is a family history of the condition, then genetic counseling will help assess risks, before planning for a child
- Active research is currently being performed to explore the possibilities for treatment and prevention of inherited and acquired genetic disorders
Current medical research has not indicated effective preventive measures for Huntington's disease, and the Dementia associated with it, since it is an inherited genetic disorder. Nevertheless, progression of the condition may be delayed or controlled, to some extent by ensuring that:
- Factors associated with diet, lifestyle, and health in general like; alcoholism, smoking, obesity, cholesterol levels, stress, nutritional deficiencies, hormonal problems, use of certain medications, diabetes, etc. may be regulated and/or controlled
- Individuals who fall in the high risk category (and all others over the age of 60 years) should be encouraged to be socially active and physically fit (with regular exercising). A healthy diet rich in fruits, vegetables, fish, whole grains, and low in fats and sugar, is recommended
- High-risk individuals should constantly maintain a healthy mind, by undertaking mentally stimulating activities like; reading/writing/teaching, solving puzzles, playing video games, listening to music, learning new skills (painting, language, playing an instrument), etc.
What is the Prognosis of Huntington Disease? (Outcomes/Resolutions)
The prognosis for an individual with Huntington disease is normally unpredictable, and based on a combination of many factors:
- Age of the adult; children with the disease, often live less longer than adults
- Degree of severity; often rapidly progressing HD bring about a speedy decline in the condition
- General health and medical history
- Tolerance level/health of the individual, when subjected to various medications; and response to dementia management
- Complications observed, if any
An early detection and aggressive management of Huntington Disease (and the dementia associated with it) should be attempted. This may prevent a rapid deterioration of the condition, and help sustain the quality of life.
Patients diagnosed with HD may live anywhere between 10-30 years following the onset of symptoms. Death usually results from heart problems, accidents, fall injuries, pneumonia, and even from suicides.
Additional and Relevant Useful Information for Huntington Disease:
There are voluntary organizations and support groups for Dementia that provides counsel, help, and understanding, to the affected individuals and their families.
What are some Useful Resources for Additional Information?
Huntington's Disease Society of America (HDSA)
505 Eighth Avenue, Suite 902, New York, NY 10018
Phone: (212) 242-1968
Toll-Free: 1 (800) 345-HDSA (4372)
(NEW HDSA HELPLINE NUMBER): 1 (888) HDSA-506
References and Information Sources used for the Article:
http://www.ncbi.nlm.nih.gov/pubmedhealth/PMH0001748/ (accessed on 2/08/13)
http://www.mayoclinic.com/health/dementia/DS01131 (accessed on 2/08/13)
http://www.alz.org/dementia/huntingtons-disease-symptoms.asp (accessed on 2/08/13)
http://www.mayoclinic.com/health/huntingtons-disease/DS00401 (accessed on 2/08/13)
http://www.ncbi.nlm.nih.gov/pubmedhealth/PMH0001775/ (accessed on 2/08/13)
http://www.hdsa.org/living-with-huntingtons/family-care/index.html (accessed on 2/08/13)
Helpful Peer-Reviewed Medical Articles:
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Morton, A. J. (2013). Circadian and sleep disorder in Huntington's disease. Exp Neurol, 243, 34-44. doi: 10.1016/j.expneurol.2012.10.014
Pogledic, I., & Relja, M. (2012). [Huntington's disease]. Lijec Vjesn, 134(11-12), 346-350.
Pringsheim, T., Wiltshire, K., Day, L., Dykeman, J., Steeves, T., & Jette, N. (2012). The incidence and prevalence of Huntington's disease: a systematic review and meta-analysis. Mov Disord, 27(9), 1083-1091. doi: 10.1002/mds.25075
Shoulson, I., & Fahn, S. (1979). Huntington disease clinical care and evaluation. Neurology, 29(1), 1-1.
Vonsattel, J. P. G., & DiFiglia, M. (1998). Huntington disease. Journal of neuropathology and experimental neurology, 57(5), 369.
Reiner, A., Albin, R. L., Anderson, K. D., D'Amato, C. J., Penney, J. B., & Young, A. B. (1988). Differential loss of striatal projection neurons in Huntington disease. Proceedings of the National Academy of Sciences, 85(15), 5733-5737.
Portera-Cailliau, C., Hedreen, J. C., Price, D. L., & Koliatsos, V. E. (1995). Evidence for apoptotic cell death in Huntington disease and excitotoxic animal models. Journal of Neuroscience, 15(5), 3775-3787.
Sugars, K. L., & Rubinsztein, D. C. (2003). Transcriptional abnormalities in Huntington disease. Trends in Genetics, 19(5), 233-238.
Vonsattel, J. P., Myers, R. H., Stevens, T. J., Ferrante, R. J., Bird, E. D., & Richardson, E. P. (1985). Neuropathological classification of Huntington's disease. Journal of Neuropathology & Experimental Neurology, 44(6), 559-577.
Rubinsztein, D. C., Leggo, J., Coles, R., Almqvist, E., Biancalana, V., Cassiman, J. J., ... & Curtis, D. (1996). Phenotypic characterization of individuals with 30–40 CAG repeats in the Huntington disease (HD) gene reveals HD cases with 36 repeats and apparently normal elderly individuals with 36–39 repeats. American journal of human genetics, 59(1), 16.