When the single diagnostic groups were taken into consideration, there was a significant difference in AQP4 levels between AD patients and the control group (AD 350.4 ± 32.7 pg/ml vs controls 209.6 ± 23.4 pg/ml, Dwass-Steel-Critchlow-Fligner test for pairwise comparisons from Kruskal–Wallis test: p = 0.046), but no other statistically significant variations were obtained (FTD vs controls p = 0.347, MCI vs controls p = 0.713, psychiatric patients vs controls p = 0.759) (Fig. 1). Here, AQP4 is linked to frontotemporal dementia.