TREM2 and frontotemporal dementia: To elucidate and reinforce the evidence of neurodegeneration and inflammation in FTD–GRN patients, we analyzed levels of neurofilament light chain (NfL), a biomarker of neurodegeneration [31], and soluble TREM2 (sTREM2), a biomarker of microglial activation [32, 33], in CSF samples of FTD–GRN patients and controls.