The true and ultimate aim of research in Huntington’s disease (HD) is to arrest the progressive neurodegeneration and thus the debilitating clinical and functional deterioration—or so it seems to those involved in the clinical care of the unfortunate individuals affected by it. Two major clinical challenges confront us: to retard, or better, to abolish disease progression in symptomatic individuals; and to prevent phenoconversion in presymptomatic individuals.

Huntington’s disease is considered to be rare, but extrapolation of its estimated prevalence—in western countries 5 to 10 per 100 000—yields for the current 25 countries of the European Union (with 455 million people in 2004) a total number of between 22 500 and 45 000 clinically affected patients in various stages of the disease. The number of presymptomatic mutation carriers is much higher. Recent advances in our understanding of the molecular pathobiology have raised hopes that rational treatments may be near. Huntington’s disease is caused by an expanded CAG triplet repeat in exon 1 of the huntingtin …