Genome-wide association studies show an increased risk of idiopathic PD with certain LRRK2 genetic variations1, 2, 3, whilst missense mutations in the catalytic core of the LRRK2 enzyme cause a familial form of PD that is largely indistinguishable from the idiopathic disease4, 5, 6. This evidence concerns the gene LRRK2 and Parkinson disease.