CHI3L1 and Alzheimer disease: In the Alzheimer’s disease continuum, higher levels of CSF YKL-40, a marker of reactive astrogliosis, have been frequently described with increased levels of p-tau27 and in associations with increased GM volume and cortical thickness in preclinical Alzheimer’s disease stages.28,29 Microglial activation, here represented by higher sTREM2 levels, has also been related to higher GM volumes in early stages of Alzheimer’s disease.11 Here, we suggest that all these pathophysiological mechanisms may be more tightly associated than previously thought.