MAPT and Alzheimer disease: Studies of AD brains report that 22 kDa tau fragments have been found to be increased in the neuronal synapses of AD subjects, that these tau fragments correlate with mitochondrial dysfunction, and have been proposed as CSF biomarkers with low specificity but high sensitivity for a variety of tauopathies including AD, frontotemporal lobar degeneration, Parkinson’s disease with dementia, and vascular dementia [3, 4, 39].