Huntington's disease is a neurodegenerative disease transmitted by dominant autosomal inheritance with complete penetration. The neurological and psychiatric signs and subsequent deterioration usually occur in adults after procuration, contributing to the persistence of this extremely debilitating disease. The gene was localized in 1983 and identified in 1993 as an increased number of nucleotide triplet (CAG) repetitions. There is clear evidence of the mutation and its clinical polymorphism. Preclinical diagnosis is possible but would raise a considerable number of questions, both in terms of ethics and practical application. Certain questions are still open to debate. What factors, probably genetic, influence the age of onset? What are the metabolic consequences of the genetic anomaly? Answers to these questions are needed for correct therapeutic management.