Initial SV2A PET studies in Alzheimer’s disease reported significant reductions in hippocampal synaptic density.13 However, a follow-up study demonstrated significant decreases in synaptic density in the entorhinal cortex, hippocampus, amygdala, lateral temporal, pre-frontal, lateral parietal and pericentral regions in Alzheimer’s disease participants.14 These findings are largely in line with our current study, which uses a highly overlapping dataset. Here, SV2A is linked to early-onset autosomal dominant Alzheimer disease.