The hallmark protein aggregates of Alzheimer’s disease (AD) are intracellular depositions of hyperphosphorylated tau (HP-tau)1 and extracellular amyloid-β plaques.2 Lewy body (LB) disease is characterized by the deposition of intracellular α-synuclein (α-syn) in the form of Lewy bodies and Lewy neurites with a typical clinical presentation of either Parkinson’s disease (PD), Parkinson's disease with dementia (PDD) or dementia with Lewy bodies (DLB). Here, MAPT is linked to early-onset autosomal dominant Alzheimer disease.