Huntington’s Disease ?>

Huntington’s Disease

What is Huntington’s Disease?

Huntington’s Disease (HD) is a brain disorder that affects a person’s ability to think, talk, and move.

The disease destroys cells in the basal ganglia, the part of the brain that controls movement, emotion, and cognitive ability. HD is caused by a mutation in a gene on chromosome 4. The job of its protein product, huntingtin, is to direct the delivery of small packages (vesicles containing important molecules) to the outside of the cell. Normally, the coding region of this gene contains the DNA sequence “CAG” repeated again and again. The number of times this triplet is repeated varies from person to person, ranging from 10 to 26 times. People with HD have an abnormally high number of these CAG triplets, approximately 40 or more. This likely disrupts the function of the gene’s protein product, but how the expansion of the CAG repeat causes disease is unknown. Somehow the brain cells of HD patients accumulate clumps of protein that become toxic, resulting in cell death. Some patients lose more than 25% of their brain cells before they die.
How do people get Huntington’s Disease?

Huntington’s disease is inherited in an autosomal dominant pattern. This means that everyone who inherits the faulty gene will eventually get the disease. A parent with a mutation in the HD gene has a 50 percent chance of passing on the disease to their children.
What are the symptoms of Huntington’s Disease?

Huntington’s disease affects the part of the brain that controls thinking, emotion, and movement. Most people who have the disease start to see symptoms between the ages of 30 and 50 (but symptoms can appear earlier or later in life). The disease gets worse over time.

Some of the symptoms include: poor memory, depression and/or mood swings, lack of coordination, twitching or other uncontrolled movements, and difficulty walking, speaking, and/or swallowing. In the late stages of the disease, a person will need help doing even simple tasks, such as getting dressed.
How do doctors diagnose Huntington’s Disease?

During pregnancy a woman can find out if her baby will have the disease with two tests: taking a sample of fluid from around the fetus (amniocentesis), or by taking a sample of fetal cells from the placenta (chorionic villus sampling (CVS)).

After the child is born, doctors can identify the disease by first doing a series of neurological and psychological tests. A genetic test can then confirm the diagnosis by determining if the person indeed has inherited the HD gene mutation (an expansion of the CAG triplet). However, the test cannot tell at what age a person will begin to get sick.
How is Huntington’s Disease treated?

Treatments do not slow the progression of the disease, but they can help make the patient more comfortable.

Medications ease feelings of depression and anxiety; others control involuntary movements.

Physical or speech therapy helps HD patients lead more normal lives.

Interesting facts about Huntington’s Disease

The disease was named for Dr. George Huntington, who first described it in 1872.

In the United States, about 1 in every 30,000 people has Huntington’s disease.

2 thoughts on “Huntington’s Disease

  1. Preimplantation genetic diagnosis

    Embryos produced using in vitro fertilization may be genetically tested for HD using preimplantation genetic diagnosis. This technique, where one or two cells are extracted from a typically 4 to 8 cell embryo and then tested for the genetic abnormality, can then be used to ensure embryos affected with HD genes are not implanted, and therefore any offspring will not inherit the disease. Some forms of preimplantation genetic diagnosis — non-disclosure or exclusion testing — allow at-risk people to have HD-free offspring without revealing their own parental genotype, giving no information about whether they themselves are destined to develop HD. In exclusion testing, the embryos’ DNA is compared with that of the parents and grandparents to avoid inheritance of the chromosomal region containing the HD gene from the affected grandparent. In non-disclosure testing, the embryo is tested in the usual way but the result is withheld from the would-be parents

    Prenatal testing

    It is also possible to obtain a prenatal diagnosis for an embryo or fetus in the womb, using fetal genetic material acquired through chorionic villus sampling. This, too, can be paired with exclusion testing to avoid disclosure of parental genotype. Prenatal testing is performed on the understanding that if the fetus is found to carry an expanded HTT gene (or, in exclusion testing, found to be at ‘high risk’), the pregnancy will be terminated

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