Huntington disease is a neurodegenerative disorder transmitted as an autosomal dominant trait. It is the first neurological disease for which presymptomatic testing has been available for 20years in France. Follow-up of mutation carriers provided a better understanding of the presymptomatic phase of the disease and will change medical practice. Studying this phase led to the identification of clinical, imaging and plasma markers prior to motor onset, which will allow finding the optimal window for preventive treatment and follow-up of its efficacy.