CHI3L1 and Parkinson disease: Other studies evaluating CSF sTREM2 have revealed increased levels in Parkinson’s disease (PD) vs. controls that also correlated with CSF α-synuclein [53] as well as in CHMP2B and GRN mutation carriers of FTD patients [54] and in CJD patients in whom levels correlated with CSF t-tau, 14.3.3 protein and YKL-40 [55].