On being an individual, or: the man in the red hat.

If health is a state of equilibrium between intrinsic (genetic) functions and extrinsic (environmental) factors, then disease can be defined as a state of disequilibrium. Medicine has traditionally emphasized extrinsic factors in the origin of human diseases; medical genetics is concerned with the intrinsic factors (mutations) that either yield disease in the universal environment or constitute states of risk for individuals in particular (or universal) enviroments. Genetic screening is a process that defines specific risks for particular individuals. Screening is an ineffective activity if there is no participation by clients. Newborn (and homozygote) screening, on the basis of an experience involving 35 million infants, is usually considered as a 'successful' enterprise. But adult screening, usually for heterozygosity, is quantitatively a much more important activity in its execution, judging from current experience. Comprehension of risk and perceived importance of biological individuality by potential participants and advocates are part of the problem. A major revision in the education of medical personnel and citizens is indicated if medical genetics is to achieve its goals.