FIGURE 1.  Graph of asymptomatic mutation carriers and estimated number of years until manifestation of HD symptoms. Age at onset was predicted by considering each subject's age and expected years until onset (y-axis) for a given CAG repeat expansion number (x-axis), according to published models (20,22,24–26). All subjects had an MMSE cognitive score—age and scholar corrected—within the reference range (18) and had minimal changes in UHDRS cognitive and MMSE scores after 2 y.