PRNP and Alzheimer disease: Previous data indicate that other IPD with extracellular PrP amyloidosis (F198S and PrP systemic amyloidosis) are associated with tauopathy with neurofibrillary tangles composed of 3R/4R tau with identical filament structures on cryo-EM to those found in Alzheimer’s disease [9, 22], compatible with similar mechanisms of amyloid-induced secondary tauopathy in certain IPD and Alzheimer’s disease.