MAPT and Parkinson disease: While inherited cases of frontotemporal dementia with parkinsonism linked to chromosome 17 emphasize the importance of pathological tau as one of the main causes of “primary tauopathies” (21, 22, 23), the association of aberrantly modified tau with the clinical and neuropathologic etiology of “secondary tauopathies” (e.g., Niemann–Pick disease type C, traumatic brain injury, and chronic traumatic encephalopathy) is more loose and mainly correlated to the presence of neuronal and/or astrocytic tau aggregates in certain brain areas (2, 17).