Other tau-PET tracers were reported to be able to differentiate patients with PSP from controls,7,8,9 but the observed binding was not confirmed to specifically relate to tau.10,11,12 The novel tau-PET tracer 18F-PI-2620 proved absent off-target binding to monoamine oxidases,13 high affinity to 3/4R tau in Alzheimer disease (AD),14 but also high affinity to recombinant 4R tau fibrils and PSP brain homogenate,13 and colocalized binding to proven 4R tau by a combination of micro-autoradiography and immunohistochemistry in PSP tissue.13 Here, MAPT is linked to early-onset autosomal dominant Alzheimer disease.