Even though plasma NfL has been shown to increase longitudinally in HD, and the associations of such longitudinal change may be of interest,6 our results suggest that a single baseline measurement of NfL has the ability to identify gene expansion carriers who have previously undergone disproportionate atrophy in the basal ganglia, and those who are likely to go on to develop similarly disproportionate atrophy in cortical and WM regions vulnerable to HD pathology. The gene discussed is NEFL; the disease is Huntington disease.