The occurrence of filamentous aggregates (fibrils) of tau and Αβ in AD, and αS fibrils in synucleinopathies such as PD and dementia with Lewy bodies (DLB), led many to examine a potential toxic and disease-causing nature of fibrils (e.g., refs. 7, –9). This evidence concerns the gene PPIB and Lewy body dementia.