LRRK2 and Parkinson disease: One novel finding of our study is the discovery that the penetrance of LRRK2 G2019S is influenced by polygenicity, with the risk of a PD diagnosis increasing 16-fold in carriers that also have a PRS within the top 25th percentile relative to non-carriers in the middle range of the PRS (i.e. 25th–75th percentile).