LRRK2 and Parkinson disease: Although longitudinal imaging data are needed to confirm this, it appears that LRRK2 mutations are protective against/compensate for both kinds of degeneration, as evidenced by larger volumes (1) compared to similarly aged healthy non-mutation carriers (pointing toward less age-related degeneration) and (2) compared to non-mutation carriers with PD (indicating less PD-related degeneration).