Analysis of The Most Important Aspects of Huntington's Disease

The World Health Organization defines Huntington's disease (HD) or Huntington's chorea as a progressive neurodegenerative disorder of autosomal dominant transmission. It is also known as 'San Vito's disease'. It owes its name to Dr. George Summer Huntington, a New York doctor who first described it in 1872 by calling it then 'hereditary chorea.' The word “chorea” comes from the Greek and means 'dance', referring to the involuntary movements characteristic of people suffering from this disease. To make knowledge of this disease easier, we will see the most significant aspects of this disease in sections: symptoms, causes, diagnosis, pathological anatomy, stages, treatment, its prevalence and investigations for its cure.

Symptoms

The symptomatology of HD is variable from one patient to another and even changes as the disease evolves. For a better understanding they can be separated into three groups:

Motor Disorders

The characteristic medical sign of this disease is chorea or involuntary movements in the patient. As the disease progresses, motor disorders become more visible, with episodes of Parkinson's appearing in advanced stages. Also noteworthy are motor disorders such as ocular motility, ataxia, speech and swallowing disorders, as well as urinary incontinence in the final phase.

Psychiatric Disorders

The most frequent psychiatric manifestation is depression. In addition, personality changes, irritability, apathy, paranoia, personal neglect and insomnia are common. Ideas about death and suicide are also frequent.

Cognitive Disorders

They consist of altered short-term memory and judgment; difficulty organizing; difficulty learning new information: slowness in processing thoughts. Dementia is developed that leads to the inability to perform the activities of daily living.

Causes

Huntington is clearly hereditary of an autosomal dominant type. The affected gene that gives rise to this pathology is HTT, located on chromosome. HTT should normally have less than 40 repetitions of the three nitrogenous bases Cytosine-Adenine-Guanine; however, when this disease occurs, much more than 40 repetitions of the triplet are observed. This gene encodes the huntingtin protein, so in the presence of EH, abnormal amounts of this protein are produced that play a fundamental role in the proper functioning of nerve fibers in the cerebral cortex. People born with this mutated gene are those who can transmit it to their offspring with a 50% probability. His inheritance does not depend on sex and does not skip generations.

Diagnosis

The mutated HD gene is present in our DNA since we were born, the clinical diagnosis of the disease is usually not reached until the first symptoms are not visible. If we have HD in our hereditary history and its symptoms manifest a series of genetic tests are done to confirm the diagnosis; If, on the other hand, the patient has no symptoms but is at risk because one of his parents has HD, he may be an asymptomatic carrier of the altered gene. In this case, the diagnosis will be based solely on the genetic test.

Pathological Anatomy

It is observable that the most affected part of the brain in patients is the caudate nucleus, a structure of the basal ganglia located in the deepest and most central region of the brain6, which controls motor coordination. This region tends to atrophy due to the loss of cortex or gray matter, thus increasing the size of the frontal antlers of the lateral ventricles. 

HD Stages

At an early stage, coordination problems appear some involuntary movements (chorea), difficulty in reasoning and often depression or irritable mood. In the intermediate stage movement disorders become more problematic, loss of speech and difficulty swallowing are noted. Already in its late stage, chorea becomes severe, practically unable to walk or speak. The patient is totally dependent on another person for their care and death from choking becomes a concern. Death in these cases does not occur because of the disease itself, but because of the complications it may have, such as asphyxiation or respiratory infections.

Prevalence

HD is distributed equally between both sexes. Its prevalence is between 5 and 10 cases per 100,000 inhabitants, something minor in East Asian and African countries. Genealogical studies allow locate the origin of the disease in Western Europe (France, Germany and the Netherlands), with subsequent dispersion to America, England, South Africa and Australia. The majors prevalence rates are given in the Maracaibo Lake region of Venezuela, on the island from Tasmania (South Australia) and Moray Firth from Scotland.  The age range in which this disease usually appears is between 30-50 years, although it can affect in other cases (10% registered) other populations such as children, adolescents and the elderly. To date in Spain there are about 4,000 people with this disease and it is estimated that 15,000 are at risk of suffering from it.

Treatment

Until now there is no cure for HD. His treatment consists of administering drugs to control problematic symptoms such as chorea. These drugs are usually generally antipsychotic, antidepressant, anxiolytic and sleeping pills. It is also recommended to attend psychotherapy sessions in order to control the depression, anxiety and apathy that characterizes Huntington's patients and that causes a high suicide rate among them. It is worth clarifying that these treatments do not improve the disease status, which continues to progress progressively, although they do improve the patient's lifestyle momentarily.

Conclusion

After knowing the general aspects of Huntington's disease we can conclude that it is a disease with little prevalence worldwide, but that its study is still important, since it is hereditary and causes a wide impact on the functional capacities of the affected person, causing movement, cognitive and psychiatric disorders. In addition, no cure is known to date, but biotechnological advances in recent years make silencing the affected gene a reality in the coming years.

References

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