Harrison's Internal Medicine Chapter 64. The Practice of Genetics in Clinical Medicine Implications of Molecular Genetics for Internal Medicine The field of medical genetics has traditionally focused on chromosomal abnormalities (Chap. 63) and Mendelian disorders (Chap. 62). However, there is genetic susceptibility to many common adult-onset diseases, including atherosclerosis, cardiac disorders, asthma, hypertension, autoimmune diseases, diabetes mellitus, macular degeneration, Alzheimer's disease, psychiatric disorders, and many forms of cancer. Genetic contributions to these common disorders involve more than the ultimate expression of an illness; these genes can also influence the severity of infirmity, effect of treatment, and progression of disease. . | Chapter 064. The Practice of Genetics in Clinical Medicine Part 1 Harrison s Internal Medicine Chapter 64. The Practice of Genetics in Clinical Medicine Implications of Molecular Genetics for Internal Medicine The field of medical genetics has traditionally focused on chromosomal abnormalities Chap. 63 and Mendelian disorders Chap. 62 . However there is genetic susceptibility to many common adult-onset diseases including atherosclerosis cardiac disorders asthma hypertension autoimmune diseases diabetes mellitus macular degeneration Alzheimer s disease psychiatric disorders and many forms of cancer. Genetic contributions to these common disorders involve more than the ultimate expression of an illness these genes can also influence the severity of infirmity effect of treatment and progression of disease. The primary care clinician is now faced with the role of recognizing and counseling patients at risk for a number of genetically influenced illnesses. Among the greater than 20 000 genes in the human genome it is estimated that each of us harbors several potentially deleterious mutations. Fortunately many of these alterations are recessive and clinically silent. An even greater number however represent genetic variants that alter disease susceptibility severity or response to therapy. Genetic medicine is changing the way diseases are classified enhancing our understanding of pathophysiology providing practical information concerning drug metabolism and therapeutic responses and allowing for individualized screening and health care management programs. In view of these changes the physician must integrate personal medical history family history and diagnostic molecular testing into the overall care of individual patients and their families. Surveys indicate that patients still turn to their primary care internist for guidance about genetic disorders even though they may be seeing other specialists. The internist has an important role in educating patients about the .
