Sporadic cases of syndromes having multiple characteristics of premature (early-onset) or accelerated (rapid-progression) aging occur in humans (85,86). It is unclear how far any of these syndromes may be regarded as a genuine acceleration of timing mechanisms that determine senescence. They are apparently pleoitropic genetic defects, and when one of the major features is accelerated aging, they are designated as progeria. One such example is Wermer's Syndrome (WS). When accelerated aging is associated with other prevalent defects, such as mental retardation and short stature, they are called progeria-like or progeroid or segmental syndromes. One example is Down syndrome (85).
Progeria syndromes do not quite duplicate all the pathophysiology of aging. Each syndrome presents an acceleration of only some of the characteristics associated with normal aging. Progeria is described as being of two main types, infantile and adult. The infantile form (Hutchinson Gilford syndrome) becomes apparent at a very early age and is associated with stunted growth, failure of sex maturation, and early signs of aging, such as skin atrophy, hypertension, and severe atherosclerosis. Death in
Hutchinson-Gilford syndrome occurs in the twenties, usually consequent to coronary heart disease. The adult form of WS resembles more closely the changes associated with aging, with respect to both the affected individual's physical appearance and the disease pattern. The onset of this premature aging syndrome occurs between the ages of 20 and 30 years, and death ensues a few years from the onset, usually due to cardiovascular disease. Tissue culture studies of fibroblasts in infantile and adult syndromes reveal that the period during which cells replicate shortens, which is interpreted as being supportive of accelerated aging (Chapter 4).
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