Langbehn DR, Stout JC, Gregory S, et al. - In this prospective study conducted at 4 academic Huntingdon disease (HD) treatment and research centers involving 2,065 visits from 443 individuals, experts summarized the decades-long early progression of Huntington disease (HD) and its dependence on CAG repeat length. Across a wide disease span, they identified motor-cognitive and white matter–ventricle summary measures with similar nonlinear trajectories, as well as a strong correlation with CAG. Furthermore, the striatum demonstrated a near-linear trajectory with strong CAG dependence, and gray matter, a slow, nonlinear pattern with a weaker dependence on CAG.