IFN-α was detected in sera from 9/36 NMO patients (5 anti-AQP4 antibody positive), significantly more than 2/41 MS patients (2/41) (odds ratio (OR) = 6.5; 95% confidence interval (CI) (1.18–64.96, P = 0.02)) (Figure 1). Here, AQP4 is linked to myeloid sarcoma.