Abstract

Medical genetics, originally an auxiliary discipline concerned with relatively rare hereditary diseases, is developing into a general approach to medical theory and practice. It encompasses not only etiological explanations of disease incidence, but methods of diagnosis, prognosis, and case management that promise an increasingly detailed and powerful knowledge of individual biology. One of the first applications of this knowledge is the use of genetic testing to obtain predictive genetic diagnosis of a growing range of conditions. ;PGD raises difficult issues because the practice is straining, or already outgrowing, existing vocabulary for social and philosophical conversations about medicine and health. Among these are notions of what biomedical science tells us about the cause of disease, what counts as a genetic disease, and what it means for a person who is not clinically sick to have a health problem on the basis of genetic information. ;This dissertation surveys three case studies---Huntington's disease , schizophrenia, and genetic approaches to common cancers---to see how medical genetics is constructing new categories of health conditions. These can be viewed as "intermediate phenotypes" from a scientific perspective, or simply as "genetic health problems" from a clinical perspective. ;For affected individuals and their families, genetic health problems pose unfamiliar problems about using genetic information, or the possibility of genetic discrimination. More fundamentally, they pose familiar problems regarding medical fidelity, the trust patients place in their physicians, and the need for moral leadership in the medical community to confirm that genetic knowledge is employed in ways that remain morally recognizable as medicine. Only by addressing these issues will we see the successful maturation of medical genetics into genetic medicine