Huntington's Disease
(Huntington Disease)
Huntington's Disease Treatment
What is the Treatment for Huntington's Disease?
Physicians may prescribe a number of medications to help control emotional
and movement problems associated with Huntington's disease. It is important to
remember however, that while medicines may help keep these clinical symptoms
under control, there is no treatment to stop or reverse the course of the
disease.
In August 2008 the U.S. Food and Drug Administration approved tetrabenazine
to treat Huntington's chorea, making it the first drug approved for use in the
United States to treat the disease. Antipsychotic drugs, such as haloperidol, or
other drugs, such as clonazepam, may help to alleviate choreic movements and may
also be used to help control hallucinations, delusions, and violent outbursts.
Antipsychotic drugs, however, are not prescribed for another form of muscle
contraction associated with Huntington's disease, called dystonia, and may in
fact worsen the condition, causing stiffness and rigidity. These medications may
also have severe side effects, including sedation, and for that reason should be
used in the lowest possible doses.
Read more in-depth information about the treatment for Huntington's disease »
Introduction to Huntington's disease
In 1872, the American physician George Huntington wrote about an illness that he called "an heirloom from generations away back in the dim past." He was not the first to describe the disorder, which has been traced back to the Middle Ages at least. One of its earliest names was chorea, which, as in "choreography," is the Greek word for dance. The term chorea describes how people affected with the disorder writhe, twist, and turn in a constant, uncontrollable dance-like motion. Later, other descriptive names evolved. "Hereditary chorea" emphasizes how the disease is passed from parent to child. "Chronic progressive chorea" stresses how symptoms of the disease worsen over time. Today, physicians commonly use the simple term Huntington's disease (HD) to describe this highly complex disorder that causes untold suffering for thousands of families.
More than 15,000 Americans have Huntington's disease. At least 150,000 others have a 50 percent risk of developing the disease and thousands more of their relatives live with the possibility that they, too, might develop
Huntington's disease.
Until recently, scientists understood very little about Huntington's disease and could only watch as the disease continued to pass from generation to generation. Families saw the disease destroy their loved ones' ability to feel, think, and move. In the last several years, scientists working with support from the National Institute of Neurological Disorders and Stroke (NINDS) have made several breakthroughs in the area of
Huntington's disease research. With these advances, our understanding of the disease continues to improve.
This information presents information about Huntington's disease, and about current research progress, to health professionals, scientists, caregivers, and, most important, to those already too familiar with the disorder: the many families who are affected by
Huntington's disease.
What causes Huntington's disease?
Huntington's disease results from genetically programmed degeneration of nerve cells, called neurons, in certain areas of the brain. This degeneration causes uncontrolled movements, loss of intellectual faculties, and emotional disturbance. Specifically affected are cells of the basal ganglia, structures deep within the brain that have many important functions, including coordinating movement. Within the basal ganglia,
Huntington's disease especially targets neurons of the striatum, particularly those in the caudate nuclei and the pallidum. Also affected is the brain's outer surface, or cortex, which controls thought, perception, and memory.
How is Huntington's disease inherited?
Huntington's disease is found in every country of the world. It is a familial disease, passed from parent to child through a
mutation or misspelling in the normal gene.
A single abnormal gene, the basic biological unit of heredity, produces
Huntington's disease. Genes are composed of deoxyribonucleic acid (DNA), a molecule shaped like a spiral ladder. Each rung of this ladder is composed of two paired chemicals called bases. There are four types of bases—adenine, thymine, cytosine, and guanine—each abbreviated by the first letter of its name: A, T, C, and G. Certain bases always "pair" together, and different combinations of base pairs join to form coded messages. A gene is a long string of this DNA in various combinations of A, T, C, and G. These unique combinations determine the gene's function, much like letters join together to form words. Each person has about 30,000 genes—a billion base pairs of DNA or bits of information repeated in the nuclei of human cells—which determine individual characteristics or
traits.
Genes are arranged in precise locations along 23 rod-like pairs of chromosomes. One chromosome from each pair comes from an individual's mother, the other from the father. Each half of a chromosome pair is similar to the other, except for one pair, which determines the sex of the individual. This pair has two X chromosomes in females and one X and one Y chromosome in males. The gene that produces
Huntington's disease lies on chromosome 4, one of the 22 non-sex-linked, or "autosomal," pairs of chromosomes, placing men and women at equal risk of acquiring the disease.
The impact of a gene depends partly on whether it is dominant or recessive. If a gene is dominant, then only one of the paired chromosomes is required to produce its called-for effect. If the gene is recessive, both parents must provide chromosomal copies for the trait to be present.
Huntington's disease is called an autosomal dominant disorder because only one copy of the defective gene, inherited from one parent, is necessary to produce the disease.
The genetic defect responsible for Huntington's disease is a small sequence of DNA on chromosome 4 in which several base pairs are repeated many, many times. The normal gene has three DNA bases, composed of the sequence CAG. In people with
Huntington's disease, the sequence abnormally repeats itself dozens of times. Over time—and with each successive generation—the number of CAG repeats may expand further.
Each parent has two copies of every chromosome but gives only one copy to each child. Each child of an
Huntington's disease parent has a 50-50 chance of inheriting the Huntington's
disease gene. If a child does not inherit the Huntington's disease gene, he or she will not develop the disease and cannot pass it to subsequent generations. A person who inherits the
Huntington's disease gene, and survives long enough, will sooner or later develop the disease. In some families, all the children may inherit the
Huntington's disease gene; in others, none do. Whether one child inherits the gene has no bearing on whether others will or will not share the same fate.
A small number of cases of Huntington's disease are sporadic, that is, they occur even though there is no family history of the disorder. These cases are thought to be caused by a new genetic mutation-an alteration in the gene that occurs during sperm development and that brings the number of CAG repeats into the range that causes disease.
Next: What are the symptoms and major effects of Huntington's disease? »
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