Predicting the future

Editor - Last month Domhnall MacAuley and Siobhan O'Neill refer to differences between single gene conditions and genes that have only a low penetrance.¹ It is this difference that the media fails to highlight; even broadsheets refer to “the gene that controls breast cancer” or even “the gene that controls heart disease.” We need to inform the media that the age of obscure single gene disorders has passed, and we now need to view diseases as multifactorial entities. It is the combination of genetic predisposition and environmental factors that cause disease. We know that hundreds and possibly thousands of genes have a direct effect on breast cancer; and it seems likely that every polymorphism in the genome has some minor, indirect effect. The BRCA1 mutation does have a relatively high penetrance, and women with the mutation may wish to have prophylactic surgery or chemotherapy. BRCA2 though has a lower penetrance, and prophylactic treatment for this may be considered inappropriate. And what of BRCA3, 4, and 5—at what level of gene penetrance should someone be labelled “at risk”? Soon environmental factors such as diet will have a greater effect on disease risk than these newly discovered mutations. The media must learn that the human genome project will not cure cancer and heart disease. certainly for the short term, our best hope is to modify environmental factors, which unfortunately means exercise and a healthy diet.

James Halpern, fourth year medical student, university of Birmingham Medical School
Email: james-halpern@hotmail.com


studentBMJ 2001;09:305-356 September ISSN 0966-6494

1. MacAuley D, O'Neill S. predicting the future. studentBMj 2001;9:290. (August.)