Huntington's Disease: Genetics, Prevalence, Life Expectancy, and Management

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Huntington's Disease: Genetics, Prevalence, Life Expectancy, and Management

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Creating a functional cure for Huntington’s disease remains a challenging objective to medical researchers today. Recent news announced that the IXICO signed a new contract for the Phase II clinical trial evaluation of safety and tolerability of a treatment for the disease.

What is Huntington’s Disease?

Huntington’s Disease is a degenerative disease, in which nerve cells in the brain break down progressively. People with this illness may develop symptoms in their 30s or 40s, but cases have been reported that signs may emerge earlier in life, referred to as juvenile Huntington’s disease. Primary disorders caused by this neurological disease are usually related to cognitive, movement, and psychiatry, and may present a wide range of signs and symptoms.

 

 

 

 

1. Movement disorders associated with Huntington’s disease include involuntary jerking or writhing movements known as chorea, problems in the muscle, such as rigidity or muscle contracture, abnormal or slow eye movements, impaired gait, posture and balance, and speech or swallowing difficulty.

2. Cognitive impairments caused by Huntington’s disease include difficulty organizing or focusing on tasks, lack of flexibility, tendency to get stuck on a thought, behavior or action, lack of impulse control which may result in outbursts, lack of awareness of one’s behavior, slow processing of thoughts, and difficulty in learning new information.

3. People with Huntington’s disease may suffer associated psychiatric disorders, such as irritability, sadness or apathy, social withdrawal, insomnia, fatigue, and suicidal thoughts. Obsessive-compulsive disorder, mania, and bipolar disorder are uncommon psychiatric disorders from the disease.

Symptoms of the juvenile Huntington’s disease include loss of previously learned skills, a significant drop in overall school performance, behavioral problems, rigid muscles affecting gait, changes in fine motor skills, which affect handwriting, tremors, and seizures.

 

 

 

 

Hereditary Background of Huntington’s Disease

Humans have two copies of a gene called Huntingtin (HTT) which codes the protein Huntingtin. A part of the Huntingtin gene is a repeated section known as trinucleotide repeat that varies in length per individual and per generation. When a dynamic mutation occurs in a healthy gene, it increases the repeat count, which results in a defective gene and if it reaches a certain threshold, it produces the mutant Huntingtin protein (mHTT). All signs and symptoms of Huntington’s disease are caused by pathological changes from the opposing functions of HTT and mHTT in the brain.

Huntington’s disease is an autosomal dominant disorder caused by an inherited defect in a single gene, which means only one copy of the defective gene to develop the illness. A person may inherit the disease with 50 percent chance if one of the parents carries the defective gene. A child who did not inherit the defective gene will never develop Huntington’s disease and cannot pass it on to their children.

A diagnostic tool is available to confirm Huntington’s disease, but people at risk face difficulty to take the genetic testing, knowing that no functional cure or effective treatment exists. Children are prohibited to take genetic testing until the age of 18, but a thorough neurological examination may be used to confirm juvenile Huntington’s disease. The medical test called pre-genetic diagnostic (PGD) can be used to test In Vitro Fertilization (IVF) to check if any implanted fertilized egg carries the abnormal gene.

Frequency

About five to seven out 100,000 individuals in western countries are affected by Huntington’s disease but a very high concentration of the disease has been found in the Lake Maracaibo region in Venezuela, where prevalence is about 700 per 100,000 individuals. In the United Kingdom, about 6,700 individuals are suffering from the disease with a prevalence rate of 12.4 per 100,000 individuals. In Australia and New South Wales, more than 1,800 individuals have the disease with an estimated 9,000 individuals at risk of developing Huntington’s disease. Some populations are less common to be affected by Huntington’s Disease, including people of African, Chinese, Korean and Japanese ancestry. One study concluded that the less cytosine-adenine-guanine repeats, different haplotypes, and CCG polymorphisms in the genetics of these ancestries may affect the chances of developing mHTT.

 

 

 


Adult individuals who suffer from Huntington’s disease have the life expectancy of 15 to 20 years after the signs and symptoms started. People with juvenile Huntington’s disease usually live 10 to 15 years after the symptoms started because of the quicker progression compared with the adult version. Mortality rate was 2.27 per million population per year caused by complications, such as pneumonia, heart disease, stroke, mental disorders, and accidents.Life Expectancy and Death Rate

Management of Huntington’s Disease

Current treatments available are designed to reduce the severity of the symptoms of Huntington’s disease and their effectiveness declines as the disease progresses.

Certain medications, such as tetrabenazine, is used to treat chorea; antiparkinsonian drugs to treat muscle rigidity; and antipsychotic drugs to treat behavioral problems.

Multidisciplinary caregiving and physical therapy are also applied for individuals with advanced Huntington’s disease.

 

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