YKL-40, as a biomarker of neuroinflammation and activation of microglia, has been assessed in a number of neurological disorders, including Alzheimer’s disease, where the pathophysiology involves pathological deposits of atypical proteins such as tau proteins, Aβ peptides, and alpha-synuclein, amongst others [193]. The gene discussed is MAPT; the disease is early-onset autosomal dominant Alzheimer disease.