Accelerated Aging: Human Progeroid Syndromes

Human aging is a complex process resulting from the interaction between a person's genetic makeup, their environment, and time. Individuals mature to adulthood, then undergo a gradual degenerative process that eventually results in death. Most of us go through these processes at roughly equivalent rates; indicating that a carefully controlled developmental program operates until adulthood. It is not clear, however, whether aging is also programmed or whether maturation is simply followed by random deterioration in the decades after our reproductive years. Such questions remain unresolved, although decreased performance of many body systems is directly related to increasing age—our bodies wrinkle and lose muscle, our hair turns gray and thins, our bones become brittle, and increasingly we succumb to age-related diseases, including cancer, diabetes, hypertension, atherosclerosis, and several neurological disorders.

Although most of us feel that we age too quickly, we should count ourselves lucky. Several human genetic diseases are noteworthy for their accelerated development of certain aging characteristics. Specifically, accelerated aging is defined as the earlier than normal onset or increased frequency of an age-related attribute or disease. Importantly, no genetic disorder exhibits acceleration of all signs of human aging. For this reason, these diseases are known as segmental progeroid syndromes, meaning each partially mimics an accelerated aging phenotype. Also, each disorder has a variable age of onset and rate of development of its distinct set of accelerated aging characteristics. Despite this variability, these syndromes provide valuable insight into the mechanisms involved in accelerated aging, and, by extrapolation, in normal human aging as well.