The significantly higher CSF sTREM2 levels in individuals with FTD but AD-like CSF (AD biomarker-positive group) than in those with non-AD-like CSF (AD biomarker-negative group), who most likely have FTLD, in our study suggests that individuals with significant neuronal injury due to AD (combined tau and amyloid pathology) may have more microglial activation and sTREM2 release into the CSF than those with FTLD. This evidence concerns the gene MAPT and frontotemporal dementia.