NEFL and Alexander disease: Plasma NfL (Fig. 1b) was increased in infantile AxD (106 pg/mL (130), P < 0.0001), juvenile AxD (21.1 pg/mL (9.6), P = 0.003), and adult AxD (24.6 pg/mL (29.6), P = 0.032) compared with controls (7.1 pg/mL (4.4)).