GFAP and Alexander disease: Plasma levels of GFAP (Fig. 1a) were significantly increased in neonatal AxD (mean (SD); 7164 pg/mL (2126), P = 0.008), infantile AxD (12,191 pg/mL (10,158), P < 0.0001), and juvenile AxD (3705 pg/mL (3018), P < 0.001) compared with controls (70.6 pg/mL (38.1)).