| It is expected by the completion of the Human Genome Project more than 100,000 human disease genes will be discovered, resulting in an increase of genes available for genetic testing. Unfortunately, not enough is known about the meaning of this genetic information and the implications of genetic testing. For example, a genetic test for one trait may later become associated with another trait. Genetic counseling protocols developed for single-gene disorders must be adapted in anticipation of new knowledge surrounding multi-disease genes. Two extensively studied multi-disease gene associations can be used to make recommendations for future pre-test and post-test genetic counseling considerations. APOE genotyping, initially associated with cardiovascular disease, has subsequently been linked to Alzheimer's disease, breast cancer, chronic traumatic brain injury and hip fractures. Mutations in the RET proto-oncogene are also associated with some familial forms of Hirschsprung's disease and multiple endocrine neoplasia type 2. |
