We conducted an in vitro autoradiography binding study with [18F]AV1451 in cases with a clinical diagnosis of SV PPA, constituting the range of underlying pathologies (i.e., TDP-43 type C, AD, and PiD) and compared binding to controls and cases with typical AD, corticobasal syndrome (CBS) due to neuropathological AD, and FTD behavioral variant (FTD-bv) due to TDP-43 type C. Coincubation with the MAO-B inhibitor deprenyl (selegiline) was performed in all cases to study MAO-B binding. This evidence concerns the gene MAOB and primary progressive aphasia.