CHI3L1 and Parkinson disease: Studies have shown that CSF levels of YKL-40 can be used to distinguish AD from non-AD dementia, Parkinson’s disease, dementia with Lewy bodies, and to distinguish between mild cognitive impairment (MCI) that progresses to AD vs MCI not due to AD indicating that CSF YKL-40 is not simply a marker for inflammation due to neurodegeneration but may be specific enough for AD [16, 17].