Certain disorders have some of the same effects as aging. Scientists study what happens in these disorders to try to learn what causes aging. For example, they identify the genes that are defective in these disorders and compare them with the same genes in older people.
(See also Overview of Aging Overview of Aging Aging is a gradual, continuous process of natural change that begins in early adulthood. During early middle age, many bodily functions begin to gradually decline. People do not become old or... read more .)
In progeroid syndromes, the aging process is greatly accelerated. Affected children develop all of the external signs of old age, including baldness, hunched posture, and dry, inelastic, and wrinkled skin. However, in contrast to normal aging, the ovaries or testes are inactive, resulting in sterility. Females have no menstrual periods. Affected children are unusually short. Thus, progeroid syndromes are not an exact model of accelerated aging.
There are several progeroid syndromes. In Hutchinson-Gilford syndrome and Werner syndrome, the central nervous system and therefore the ability to do many daily activities are largely unaffected unless a stroke Overview of Stroke A stroke occurs when an artery to the brain becomes blocked or ruptures, resulting in death of an area of brain tissue due to loss of its blood supply (cerebral infarction) and symptoms that... read more occurs.
Hutchinson-Gilford syndrome begins in early childhood. It is caused by a genetic abnormality but is usually not inherited. That is, the genetic abnormality (mutation) occurs on its own. It causes inelastic and wrinkled skin, baldness, and other problems usually associated with aging (such as disorders of the heart, kidneys, and lungs and osteoporosis Osteoporosis Osteoporosis is a condition in which a decrease in the density of bones weakens the bones, making breaks (fractures) likely. Aging, estrogen deficiency, low vitamin D or calcium intake, and... read more ). The body does not grow normally and thus appears too small for the head. Most children with Hutchinson-Gilford syndrome die in their teens. The cause is usually a heart attack or stroke. The mutation that causes this disorder has been identified, and a clinical trial of an inhibitor of the faulty gene has had encouraging results.
Werner syndrome, a hereditary syndrome, begins in adolescence or early adult life. It causes inelastic and wrinkled skin, baldness, and problems associated with aging, including
Down syndrome Down Syndrome (Trisomy 21) Down syndrome is a chromosome disorder caused by an extra chromosome 21 that results in intellectual disability and physical abnormalities. Down syndrome is caused by an extra chromosome 21... read more is much more common than progeroid syndromes Progeroid Syndromes Certain disorders have some of the same effects as aging. Scientists study what happens in these disorders to try to learn what causes aging. For example, they identify the genes that are defective... read more . It also causes problems typical of old age in younger adults:
In contrast to progeroid syndromes, Down syndrome greatly impairs the central nervous system. It usually causes intellectual disability and, later in life, symptoms of Alzheimer disease Symptoms Alzheimer disease is a progressive loss of mental function, characterized by degeneration of brain tissue, including loss of nerve cells, the accumulation of an abnormal protein called beta-amyloid... read more . Also, brain tissue, obtained during an autopsy and examined under a microscope, has the same type of degeneration that is seen in people with Alzheimer disease.