CHI3L1 and early-onset autosomal dominant Alzheimer disease: YKL40 is a robust CSF biomarker in other neuroinflammatory diseases, such as Creutzfeld-Jakob and Alzheimer’s disease (Baldacci et al, 2019; Llorens et al, 2017; Mavroudis et al, 2022), and the mouse homolog of human YKL40, CHI3L1, was elevated in brains of LD and APBD models and expression was normalized in rescued LD (DKO) mice.