Wilson EN, Swarovski MS, Linortner P, et al. - Given the onset of cognitive decline in Parkinson disease may be related to the appearance of pathological amyloid-β and/or tau, and given the known link of microglial activation with advancing Parkinson disease, researchers undertook this cross-sectional analysis to inquire if CSF and/or plasma soluble form of the triggering receptor expressed on myeloid cells 2 (sTREM2) varied between CSF biomarker-defined Parkinson disease participant subgroups. Participants were 165 individuals, including 17 cognitively normal elderly, 45 patients with Parkinson disease without cognitive impairment, 86 with mild cognitive impairment, and 17 with dementia. On stratification of participants by CSF amyloid-β and tau levels, it was identified that there were high CSF sTREM2 levels in Parkinson disease subgroups with a positive tau CSF biomarker signature, but not in Parkinson disease subgroups with a positive CSF amyloid-β biomarker signature. Overall, CSF sTREM2 could be a surrogate immune biomarker of neuronal injury in Parkinson disease.