tailieunhanh - Chapter 064. The Practice of Genetics in Clinical Medicine (Part 7)

Therapeutic Interventions Based on Genetic Risk for Disease Specific treatments are now available for an increasing number of genetic disorders, whether identified through population-based screening or directed testing (Table 64-2). Although the strategies for therapeutic interventions are best developed for childhood hereditary metabolic diseases, these principles are making their way into the diagnosis and management of adult-onset disorders. Hereditary hemochromatosis illustrates many of the issues raised by the availability of genetic screening in the adult population. For instance, it is relatively common (approximately 1 in 200 individuals of northern European descent are homozygous), and its complications are potentially preventable. | Chapter 064. The Practice of Genetics in Clinical Medicine Part 7 Therapeutic Interventions Based on Genetic Risk for Disease Specific treatments are now available for an increasing number of genetic disorders whether identified through population-based screening or directed testing Table 64-2 . Although the strategies for therapeutic interventions are best developed for childhood hereditary metabolic diseases these principles are making their way into the diagnosis and management of adult-onset disorders. Hereditary hemochromatosis illustrates many of the issues raised by the availability of genetic screening in the adult population. For instance it is relatively common approximately 1 in 200 individuals of northern European descent are homozygous and its complications are potentially preventable through phlebotomy Chap. 351 . The identification of the HFE gene mutations of which are associated with this syndrome has sparked interest in the use of DNA- based testing for presymptomatic diagnosis of the disorder. However up to one-third of individuals who are homozygous for the HFE mutation do not have evidence of iron overload. Consequently in the absence of a positive family history current recommendations include phenotypic screening for evidence of iron overload followed by genetic testing. Whether genetic screening for hemochromatosis will someday be coupled to assessment of phenotypic expression awaits further studies. In contrast to the issue of population screening it is important to test and counsel other family members when the diagnosis of hemochromatosis has been made in a proband. Testing allows the physician to exclude family members who are not at risk. It also permits presymptomatic detection of iron overload and the institution of treatment phlebotomy before the development of organ damage. Table 64-2 Examples of Genetic Testing and Possible Interventions Genetic Disorder Inherita nce Genes Interventions Oncologic Hereditary nonpolyposis colon AD .