[Huntington's disease: ethical aspects of presymptomatic testing].

Huntington's disease is an autosomal dominant entity with onset mostly in middle age. Neurological signs and psychosis evolve without possibility of treatment or alleviation. Genetic counseling of relatives of patients has changed since the development of presymptomatic testing. Ethical issues and dilemmas associated with the application of this technological advance are reviewed as a result of a request by a mother to perform presymptomatic testing in her young daughter whose father has Huntington's disease.