MAPT and Alzheimer disease: We investigated whether CSF PGRN (i) increases in relation to the clinical course of AD; (ii) is associated with cognitive impairment and neuroimaging markers of neurodegeneration (fludeoxyglucose positron emission tomography, FDG‐PET and hippocampal volume) in subjects with AD; and (iii) is associated with the microglial‐derived protein sTREM2 as well as biomarkers of amyloid and tau pathology.