Genetic counselling for unaffected family members

This chapter focuses on aspects of genetic counselling for those at 50 per cent risk for Huntington’s disease (HD). There are various options including not being tested. Predictive testing for HD is described together with some perspectives from patients. There are four types of results from a predictive test: normal, intermediate allele, reduced penetrance, and abnormal. The implications of these are discussed. Options regarding testing in pregnancy are discussed which include: no testing and accepting a risk, invasive tests such as chorion villus sampling or amniocentesis and preimplantation genetic diagnosis. Finally, the issue of testing someone at 25 per cent risk is discussed.