LRRK2 and Parkinson disease: Mechanistically, given that LRRK2 sits at the interface between PD and CD and that studies have shown increased LRRK2 levels in peripheral immune cells of PD patients74 or in inflamed colonic tissue of CD patients72, future studies should directly investigate the role that LRRK2 plays in the gut–brain axis in PD and how LRRK2 synergizes with intestinal inflammation to promote neuroinflammation and neuropathology associated with PD.