Huntington's Disease
What is Huntington's Disease?
Huntington's disease, otherwise known as HD, is the result of a genetic disorder in which the deterioration of brain cells, called neurons, occur in certain areas of the brain. This degeneration causes uncontrolled movements, loss of reasonable abilities, and emotional disturbance. Specifically affected are cells of the basal ganglia, structures deep within the brain that have many important functions, including coordinating movement. HD is a familial disease, passed along from parent to child through an alteration in the normal gene. Genetic tests, along with a complete medical history and neurological and laboratory tests, help physicians diagnose HD Pre-symptomatic testings are available for individuals who are at risk for carrying the HD gene.
Causes
Huntington’s
disease is a genetic disorder that can be passed from parent to child. Each
child of a parent who has HD has a 50/50 chance of inheriting the HD gene.
If a child does not inherit the HD gene, he or she will not develop the disease
and cannot pass it to following generations. In 1 to 3 percent of individuals
with HD, no family history of HD can be found. 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 gender of the individual. This pair has two X chromosomes in females and
one X and one Y chromosome in males. The gene that produces HD lies on chromosome
4, one of the 23 pairs of chromosomes, placing men and women at equal risk
of acquiring the disease. Within the basal ganglia, HD especially targets
neurons of the striatum. Also affected is the brain's outer surface, or cortex,
which controls
thought, perception, and memory.
Symptoms
Some early
symptoms of HD are mood swings, depression, irritability, trouble driving,
problems
learning and remembering facts, or making decisions. As the disease progresses,
concentration on logical tasks becomes increasingly difficult and the patient
may have difficulty feeding him or herself and swallowing. The rate in which
the disease progresses and the age of instigation will vary from person to
person.
Treatment
Physicians
prescribe a number of medications to help control emotional and movement problems
associated with HD. Most drugs used to treat the symptoms of HD have side
effects such as fatigue, restlessness, or hyper excitability. It is extremely
important for people with HD to maintain physical fitness as much as possible.
Individuals who exercise and keep active tend to do better than those who
do not.
Research
Scientific investigations are using electronics and other technologies to enable scientists to see what the defective gene does to various structures in the brain and how it affects the body's chemistry and metabolism. Laboratory animals are being bred in the hope of duplicating the clinical features of HD so that researchers can learn more about the symptoms and progression of HD. Investigators are implanting fetal tissue in rodents and nonhuman primates with the hope of understanding, restoring, or replacing functions typically lost by neuronal degeneration in individuals with HD.
Normal
Brain
Diseased Brain
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