MAPT and early-onset autosomal dominant Alzheimer disease: LBD is clinically diagnosed as Parkinson’s disease when initially manifesting as bradykinesia and rigidity, or as dementia with Lewy bodies (DLB) when cognitive impairment occurs before the onset of motor symptoms.1,2 While limbic and neocortical alpha-synuclein are thought to drive cognitive impairment in LBD,3-5 concomitant Alzheimer’s disease pathology [β-amyloid (Aβ) plaques and tau neurofibrillary tangles] is frequently seen at autopsy in individuals with LBD.