Cerebrospinal fluid (CSF) concentrations of YKL-40 are significantly increased in sporadic Creutzfeldt-Jakob disease (CJD) and Alzheimer’s disease (AD), while other neurodegenerative dementias such as frontotemporal dementia (FTD), Lewy body dementia (LBD) and vascular dementia (VaD) show normal to slightly altered levels [4–6]. This evidence concerns the gene CHI3L1 and early-onset autosomal dominant Alzheimer disease.