CHI3L1 and early-onset autosomal dominant Alzheimer disease: In addition, Chi3l1 expression was studied, as it was also upregulated in the aforementioned RNAseq study and because its human homolog, YKL40, is a leading CSF biomarker in other neuroinflammatory and neurodegenerative diseases such as Creutzfeld-Jacob and Alzheimer’s disease (Baldacci et al, 2019; Llorens et al, 2017; Mavroudis et al, 2022).