[Psychiatric and ethical aspects of genetic diagnosis exemplified by Huntington chorea].

Huntington's disease is an autosomally dominant, inherited neurodegenerative disorder. Depression, psychotic syndromes, and personality changes are common psychiatric features, frequently occurring before the onset of characteristic motor symptoms. Since 1993, direct genetic testing has been available, which provides predictive diagnosis even in neurologically asymptomatic persons at risk. The prediction of this devastating disease constitutes a massive psychological burden. In particular, since possibilities of prevention or causal therapy are still not known, ethical aspects are of considerable importance. This refers for example to preimplantation diagnostic testing or the testing of children. Besides, it is important to consider paranoid or depressive symptoms restricting the competence of decision making for genetic testing. Early-onset cognitive deficits may also lead to fundamental disability in understanding. In addition, informed consent may be complex due to social or familial issues which may interfere with the autonomy of the applicant. In these circumstances, the counselor may clash between the principle of beneficence/nonmaleficence and respect for the autonomy of the applicant. In the future, genetic tests will be used for an increasing number of inherited diseases; it is therefore necessary to learn from experiences in the predictive testing of Huntington's disease and to develop ethical codices that can be transferred to the practice of counseling in other genetic disorders.