LRRK2 and Parkinson disease: Although the endocytosis of α-syn containing RBC-EVs and increased kinase activity of LRRK2 have been proved to be highly associated with the hyperactivation of PD monocytes, the precise mechanisms involved in the hyperactivation of PD monocytes, including those beyond endocytosis of RBC-EVs and kinase of LRRK2, need to be investigated further.