As the immune system mediates a host’s response to its environment, and PD has long been considered a multifactorial disorder30, it is attractive to hypothesize successive periods of inflammation and LRRK2 activation may explain the penetrance of LRRK2-parkinsonism, and such a mechanism may partially underlie the ontology and incidence of idiopathic PD that is steadily increasing. Here, LRRK2 is linked to Parkinson disease.