MAPT and Alzheimer disease: In these two forms of amyloidosis [referred herein as PrP-CAA (Q160X) and GSS (F198S)], APrP coexists with numerous Tau neurofibrillary aggregates made of 3R- and 4R-Tau isoforms, suggesting that different amyloids may share pathogenetic mechanisms leading to Tau aggregation in AD, PrP-CAA, and GSS.