GBA1 and Parkinson disease: If similar in humans, the increased spread of α-syn pathology in PD patients with GBA mutations might explain the earlier age of onset, the increased cognitive decline (3, 4, 53, 54) and greater cortical burden of Lewy bodies observed in PD patients with GBA mutations (3), in addition to GBA mutations increasing the risk of developing PD with dementia and dementia with Lewy bodies (55).