Huntington's Disease

Topics: Huntington's disease, Genetic disorder, Genetics Pages: 31 (7003 words) Published: December 29, 2013
Introduction
What Causes Huntington's Disease?
How is HD Inherited?
What are the Major Effects of the Disease?
At What Age Does HD Appear?
How is HD Diagnosed?
What is Presymptomatic Testing?
How is the Presymptomatic Test
Conducted?
How Does a Person Decide Whether to be
Tested?
Is There a Treatment for HD?
What Kind of Care Does the Individual with
HD Need?
What Community Resources are Available?
What Research is Being Done?
Molecular Genetics
The HD Gene and Its Product
Cell Death in HD
Animal Models of HD
Fetal Tissue Research
Clinical Studies
Imaging
How Can I Help?
What is the Role of Voluntary
Organizations?
Where can I get more information?
Glossary
Introduction
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 HD. 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 HD.
Until recently, scientists understood very little
about HD 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 HD research. With these advances,
our understanding of the disease continues to
improve.
This brochure presents information about HD,
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 HD.
What Causes Huntington's Disease?
HD 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, HD 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 HD Inherited?
HD 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 HD. 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...
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