While the CHIT1, CHI3L1, and CHI3L2 expression levels tend to increase in the brain of AD patients, most likely because they are linked to neuroinflammation and innate immune cell activation, in the opposite manner, the CHID1 levels tend to decrease, and we hypothesized this is because they are linked to neuron death. This evidence concerns the gene CHI3L1 and Alzheimer disease.