C9orf72 and Atrophy: The observation that C9orf72+ showed only a small degree of acceleration yet the degree of volume loss accumulated was close to the amount seen with GRN+ in the symptomatic phase might suggest that atrophy starts at a younger age, which is supported by previous studies.6,12 Furthermore, studies15,47,48,49 of small cohorts of C9orf72+ have highlighted slow progression with insidious transition from presymptomatic to symptomatic phases.