Rare Genetic Diseases
Genetic diseases are caused by irregularities in a person's chromosomes. Both inherited characteristics and environment can have a part in developing a genetic disease. With new discoveries in mapping the human genome, medicine is now making more progress in identifying the genes responsible for more and more rare genetic diseases, which often are the result of the mutation of a single gene.
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Facts
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Genetic disorders usually are caused by a change in the DNA (deoxyribonucleic acid). Change in DNA results in change in RNA (ribonucleic acid), and then a change in proteins, which send signals between cells. Depending on how the body's proteins are affected, the mutations result in genetic diseases. Some are more serious than others.
Significance
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Rare genetic disorders are difficult for any family to handle, especially when they affect children. Some people with a history of genetic disease in the family---and even some who don't---go to genetic counseling when thinking about becoming pregnant, in order to gauge the possibility of passing on a rare genetic disease.
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Types
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Several different types of genetic diseases exist. Progeria is a very rare disease that causes rapid aging. It is only seen in one in four million babies. Another is Noonan Syndrome, which results in unusual facial features, short stature, and heart problems. Noonan Syndrome is seen in 1 in 1000 to 2500 babies.
Time Frame
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Many rare genetic disease are apparent at or before birth but some take time to develop. Newborns can be screened for some genetic diseases that may not yet be visible. In the U.S., it is common to test children at birth for phenylketonuria, a disease that results in mental retardation if it is not caught and treated early, as well as congenital hypothyroidism. Carrier testing can be done before a woman gets pregnant to see if either prospective parent carries a copy of a gene mutation.
Features
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Rare genetic diseases usually feature physical abnormalities. Fragile X Syndrome results in differing facial features, a larger-than-average head size, and protruding ears, forehead and chin. Tuberous sclerosis, which causes epileptic seizures and tumors throughout the brain and organs, shows itself in skin lesions, rashes and strange de-pigmented leaf shapes on the face and body.
Effects
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Different diseases have different effects. Lowe Syndrome is seen only in males. It causes mental retardation, cataracts and, later, glaucoma. People with Lowe Syndrome also commonly develop kidney disease. Tay-Sachs disease progresses slowly, from no visible symptoms to seizures to complete destruction of the nervous system. Tay-Sachs Disease is fatal.
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