NPC1 and Niemann-Pick disease, type C1: The mean level for NfL in the NPC1 cohort (n = 118) was 27.0 ± 30.9 pg/mL (median [IRQ] 17.0 [11.4-23.3] pg/mL) and the mean level of NfL in the control group (n = 24) was 4.4 ± 1.6 pg/mL (median [IRQ] 4.3 [3.4-5.0] pg/m[), representing a 6.1-fold increase in mean levels of NfL in serum from individuals with NPC1 compared with pediatric controls.