LRRK2 and Alzheimer disease: From a neuropathological point of view, accumulation of intracellular tau protein is seen in both AD and FTD [2]; moreover, TAR-DNA binding protein (TDP)-43 deposition has been reported in AD, in a subtype of FTD and, in some rare PD cases, associated with a leucine-rich repeat kinase 2 (LRRK2) mutation [3,4].