LRRK2 and Parkinson disease: We also investigated G×G between well-known PD mutation p.G2019S in the LRRK2 gene (equivalent to SNP rs34637584) and both, 90 previously reported PD risk SNPs and SNPs from a 1 Mb region on either side of SYT10. Among IIPDGC cases, p.G2019S had a very low frequency of 0.007, and only few centers reported enough mutation carriers to allow sensible inclusion in the meta-analysis.