Further, increased AQP4 in CSF or blood has been noted in other conditions like intracerebral hemorrhage and even Alzheimer’s disease (where AQP4 variants correlate with amyloid clearance), underscoring a growing recognition of AQP4’s potential as systemic biomarkers [49,50]; however, more robust studies are required to properly validate its use. Here, AQP4 is linked to early-onset autosomal dominant Alzheimer disease.