In Chapter 4 we have discussed a variety of potential applications of genetic science in the treatment and prevention of disease. Many of these applications are still at the research stage; at present, the application of genetics in health services is largely confined to services for individuals and families affected by – or at risk of – relatively rare Mendelian diseases, chromosomal disorders, syndromes or congenital abnormalities. In this chapter we first review these services and then outline some of the challenges for service development that are likely to emerge in the coming decades as research on the genetic contribution to common disease begins to bear fruit.

It is important to keep in mind that, although individually rare, Mendelian diseases and chromosomal disorders collectively account for a significant burden of mortality and morbidity, especially in children. The genetic cause of around 1800 single-gene or chromosomal disorders is now known, and the number continues to grow rapidly. As knowledge has grown about single-gene causes of common disease such as breast cancer, increasing numbers of individuals have identified themselves as potentially at risk on the basis of their family history, and sought advice from genetics specialists. The workload of clinical geneticists, laboratory geneticists and genetic counsellors has grown at a rapid rate. It is vital, therefore, that funding for clinical genetics services is protected and that provision is made for the introduction of validated new tests and technologies as they become available, to improve services for patients.