MAPT and Parkinson disease: Whilst all LRRK2-PD patients display neuronal loss in the SNpc, around 50% of patients do not show any apparent LB pathology, with variable tau pathology in most cases (Poulopoulos et al., 2012; Kalia et al., 2015; Schneider and Alcalay, 2017; Agin-Liebes et al., 2019; Henderson et al., 2019; Kalia, 2019).