Senescence. Pathology facing medicine's ultimate issue

Classic pathology tends to view old age as a composite of familiar, though not necessarily observable lesions. Modern gerontological research, in contrast, portrays chronic-progressive diseases that emerge from adulthood onward as mere complications of a universal condition called "aging." To integrate this view into both teaching and practice is the task faced by the pathologist interested in aging. The essay reviews current procedures used to estimate biological age (ie, to quantitate discrepancies between chronological and biological age), and the conceptual basis of these procedures. In addition, a new definition of aging is proposed: a time-dependent, irreversible shift from environmental to intrinsic causation of disease. This intrinsic pathogenesis has two components. The first is genetic and beyond the reach of contemporary health care. The second, more difficult to define, entails the growing number of degenerative lesions due to viral agents, as well as carcinogenesis. The conventional dichotomy between a malleable environment and an impregnable genome is blurred. Significant advances are more likely in the increasingly complex frontier area between them than within the genome itself.