Presymptomatic detection of Huntington's disease.

Because of the usually late onset of Huntington's disease (HD) most sufferers have reproduced and passed the HD gene to about one half of their offspring before they themselves develop symptoms of the disease. Genetic counseling of persons at risk of HD would be greatly facilitated if the gene could be detected presymptomatically. At present, there is no suitable predictive test for HD, but many approaches currently being investigated show some promise. These approaches are reviewed and critically evaluated.