Advances in the understanding of the genetic causes of some neuropsychiatric disorders are having an impact on clinical practice as direct mutation analysis becomes possible. Mutation analysis is now available in UK Health Service diagnostic laboratories for Huntington's disease (HD) and the fragile X syndrome (FRAXA). Psychiatrists need to be familiar with issues surrounding presymptomatic and diagnostic testing in HD and diagnostic and carrier testing in FRAXA. They may be asked to assist clinical geneticists in the assessment of candidates for HD presymptomatic testing and a suggested mode of assessment is described here. The procedure for HD will provide the model for use with other familial neuropsychiatric disorders of late onset, notably familial Alzheimer's disease (FAD). Testing for FAD is already possible in conjunction with research laboratories in the few families where a mutation has been discovered and we shall have more tests for FAD within a few years.
The new genetics in psychiatry
