Huntingtons Chorea

A report by Connor Fenwick and Mason Gray


Nature of the Genetic Difficulty

Each person has 46 chromosomes 23 from the mother and 23 from the father. There are two types of chromosomes autosomal which are the first 22 pairsand and sex chromosomes, which are the 23rd pair. Since Huntington disease is autosomal dominant, this means the gene involved is on an autosomal chromosome. And recently has been localized on the fourth autosomal chromosome pair. People who have the disease have an HD gene that is not functioning correctly and expresses itself in a strong way or “dominates” the other working gene. Since it is not on one of the sex chromosomes, it can affect both males and females. Both males and females have the exact same chance of having an infected child.

The gene for Huntington disease on the fourth chromosome has been characterized in recent years. The chromosome is composed of genes and each gene is composed of a string of molecules called nucleotides. The nucleotides are adenine cytosine guanine and thymine . The gene is made up of a series of three nucleotides which form the structure of DNA in the gene and each gene has its own specific sequence of base pairs. In Huntington disease the DNA sequence cytosine adenine guanine (CAG) is a part of this sequence Individuals with Huntington disease may have from 40 to over 100 repeated CAG segments. It is not known how this repeated sequence causes Huntington disease but research to develop therapies to treat Huntington disease is still being continued.

Basis Facts of Disease

Huntington’s Chorea is an inherited neurodegenerative genetic disorder that affects the muscle coordination of the afflicted patient. The disease also leads to the decline of the mental state and health of the patient’s brain that can induce severely harmful psychiatric problems. The degeneration of neurons in the brain causes the person to loose motor control, mental capacity and often their memories as well.

Huntington’s chorea is often hard to detect as it typically begins to show symptoms around age thirty, and at that point there is not much that can be done for the afflicted person. In fact there is no way to know if a person has Huntington’s disease unless a person knows that someone in his or her family had it. If person’s parents have it there is a 50% chance that the disease as well as a 50% chance that you would pass it on to your child may affect someone. Most people with Huntington's disease develop signs and symptoms in their 40s or 50s, but the onset of disease may be earlier or later in life. When disease onset begins before age 20, the condition is called juvenile Huntington's disease. Earlier onset often results in a somewhat different presentation of symptoms and faster disease progression.

Some symptoms of the disease include intense depression, irritability, jerky and strange movements that typically some one would see in OCD (such as obsessive hand washing, scratching at eyes). Some other symptoms would be involuntary muscle spasms that can be very dangerous to the afflicted, learning inefficiencies. Also typically in late onset Huntington’s the patient will show psychological decline (in my uncle jakes case, talking to himself and his “ friend” who told him to do things” and eventually the patient wont be able to perform basic actions. The retrogression of motor control typically follows a certain pattern. 1. Loss of appetite 2. Bowel control 3. Basic movements 4 memory 5 breathing.


Currently for Huntington’s Chorea there is no cure. However while there is no means of preventing the contraction of the disorder, there are means by which some one afflicted with the disease can slow its progress. Some methods meant to help an individual deal with the effect of the disease include, physical therapy, speech therapy and psychiatric counseling. Some drugs also have been approved by the FDA that help minimize the severity of the muscle spasm suffered by patients who have Huntington’s. This drug is called tetrabenazine and was approved august of 2008. Some other drugs that help reduce the random spasms of the muscles (chorea) are Neuroleptics and benzodiazepines, while these drugs cant cure the disease by any manner; they can help alleviate the patient of some of the spasms and effects. As of now there has been no method conceived by scientists that would slow down the neuron degeneration in the brain.

Sources Cited