The obvious participation of AQP4 in CSF transport in the brain and interstitial fluid clearance as a key element of the glymphatic system, as well as the lack of reliable biological markers in the differential diagnosis of iNPH and AD, lead to the conclusion that brain AQPs might be involved in the development of these pathological conditions and might help monitor and differentiate the two diseases. This evidence concerns the gene AQP4 and Alzheimer disease.