Huntington’s Part Three!!!

Huntington’s is a progressive neurodegenerative disease that causes specific nerve cells to waste away. Currently there is no cure for Huntington’s and no way to stop the disease from getting worse. Treatments focus on slowing the course of the disease and treating the individual symptoms. Conventional antipsychotic drugs like haloperidol can be used to try and control extra movements but the use of such drugs can lead to the development of tardive dyskinesia so the are generally only recommended in the chorea is completely debilitating. Dopamine agonists can also be used to treat irregular movements. All medications should be prescribed at the lowest dose possible and patients should be periodically taken off their medications (drug holidays).
There are 5 main ways that the research on Huntington’s is being conducted. Basic neurobiology is when the scientists study the specific gene to see how it is affecting the body. They can also use imaging to identify the structures in the brain that are most affected by the mutated Huntington’s gene. Imaging is generally carried out through the use of PET scans. Animal models are bred to show the clinical symptoms of Huntington’s in order to observe the progression of the disease. Animal models have also been used to study the effectiveness of fetal tissue in restoring or replacing functions lost by nerve degradation. The final pathway fro studying Huntington’s is through genetic studies that look at markers and inheritance factors within families.
Recent studies suggest that co-enzyme Q10 may help slow down the course of the disease. There is currently a study being conducted by Mass Gen and the National Institute of Neurological Disorders and Stroke to determine if coenzyme Q10 is effective in slowing the effects of Huntington’s disease. He study is also looking at the practicality of the drug as a treatment and whether it is safe or not. Looking at an actual ongoing research study was interesting because I got to see the research precautions that had been discussed in my seminar actually used in an actual research setting. For example the allocation of the co enzyme and of the placebo was randomized and the masking used was double blind meaning that neither the subject, caregiver nor investigator actually knew for certain which subject was given which drug.
Other areas that are currently being studied in relation to Huntington’s are its excitotoxicity (the over-stimulation of cells by natural chemicals found in the body), defective energy metabolism (a defect in the mitochondria), oxidative stress (normal metabolic activity in the brain that produces toxic compounds called free radicals) and tropic factors (natural chemical substances found in the human body that may protect against cell death). Hoprefully advancements in any one of these areas will lead to a break through in the study of Huntington’s.

Huntington’s Part Two!

The testing for Huntington’s disease is relatively simple but the results can lead to serious ramifications. A blood sample is used to count the number of CAG repeats on chromosome 4. There are three types of testing for Huntington’s. Presymtopatic is when the person has a family history of Huntington’s but is currently expressing not symptoms, confirmatory testing is used to determine whether a person already showing symptoms of Huntington’s actually has the disease and prenatal testing is done to determine if a fetus is at risk for HD.
The test itself is simple but the decision to undergo testing is a multi step process, which includes a neurological examination, pretest counseling and a follow up. The neurological exam is used to determine whether the person is actually showing symptoms and therefore if the test is really merited. The counseling explains to the person being tested about the disease, their level of risk and about the testing procedure as well as the test’s limitations and it’s accuracy. If the person decides that testing ids the next step and team of neurologists, genetic counselors, social workers and psychiatrists is assembled to help the person decide they are certain they want to undergo testing and to ultimately prepare them for the results.
People may choose to undergo testing even if they are showing no symptoms so that they can make more informed decisions about their futures or to settle any doubts. Some choose not to be tested in order to avoid loss of employment or medical coverage. Genetic counseling is often used by a family with a history of the disease who are considering having children. Testing is generally not recommended for patients under the age of 18 unless they have very compelling symptoms.
The test for Huntington’s can run between 600 to 1,500 dollars however it is generally advised to wait to submit the claim until after the results of the test come back negative. The discovery of a mutated Huntington gene can be considered a pre-existing condition and ca be used as grounds for denying medical coverage. In some states laws to exist that prohibit genetic discrimination and there is currently a federal law being considered that would do the same.

Huntington’s Part One!

Although I realize the ridiculousness of my first blog post after school has officially started it really has been a busy summer! In this post I’m going to give a summary of all the different aspects of Huntington’s. In my second post I will look at the ethical issues associated with the testing for Huntington’s and it’s path of inheritance and in my third I will talk about various new drug trials, treatments and the research currently going on.
What really stunned me most about my research this summer was the pure magnitude of the information known about Huntington’s. I expected it to still be a rather mysterious disease since there seems to be such confusion surrounding how best to treat it. Although lots is known about the disease there are several key problems with truly identifying the root of the disease.
Huntington’s is caused by a genetic defect on chromosome four. A section of the DNA strand is repeated more often than it should be. As the gene is passed on the number of repeats on the strand tends to grow longer which means the symptoms of Huntington’s begin to appear at younger and younger ages. If one of your parents has Huntington’s you have a 50% chance of inheriting the gene. The exact function of the huntingtin protein is unknown but it seems to play a role in nerve cells. The defect on chromosome 4 causes the protein to become malformed and become prone to clumping in the brain, which leads to the death of many nerve cells. The mutant protein accumulates abnormally throughout the entire body but only kills cells in the corpus striatum.
The most affected areas in the basal ganglia and the cortex the areas of the brain that controls movement and thoughts are the most affected areas of the brain. Within the basal ganglia Huntington’s especially targets the neurons of the striatum particularly the nerve cells of the caudate and the pallidium which are both very important parts of the brain.
All of these factors eventually manifest as behavioral and movement problems. The behavioral problems generally appear before the movement issues and can include antisocial behavior, hallucinations, moodiness, paranoia and psychosis. Movement symptoms can include head turns in order to shift eye position, facial ticks, unsteady gait, and quick or jerky movements of the arms, legs and other body parts. Patients generally die within 15 or 20 of symptoms appearing but they rarely die from the actual disease. Infection is generally the cause of death is common but suicide is also common.

The Mechanisms of Huntington’s Disease

karyotype

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