CHI3L1 and Alzheimer disease: Increased CSF YKL-40 levels have been reported in multiple AD cohorts [29–34], and in frontotemporal dementia (FTD) cases [34–36] but not in vascular dementia (VaD) and in DLB/PDD [32, 35], indicating that its deregulation is associated with disease-specific alterations and further suggesting that elevated CSF YKL-40 levels is not a specific signature for AD pathogenesis.