In Alzheimer disease patients, MAPT/tau pathology and granulovacuolar degeneration bodies (GVBs) co-occur in the same brain regions and in the same cells. The interdependence of these neuropathological hallmarks and the identity of GVBs have long been elusive. Recently, we showed that MAPT pathology causes GVB formation in neurons in vivo and in vitro. Using these novel GVB models, we identified GVBs as lysosomal structures at the convergence of the endo- and autolysosomal pathways. Here, the possible functional consequences of neuronal GVB formation are discussed.