At baseline, NfL concentrations did not differ significantly between Huntington’s disease gene carriers and controls, but were elevated among prodromal/manifest Huntington’s disease gene carriers at 12-year follow-up compared to both controls and gene carriers who had remained premanifest (Supplementary Table 9; F(2,23) = 14.7, P = 0.003, ηp2 = 0.51). The gene discussed is NEFL; the disease is Huntington disease.