Leucine-rich repeat kinase 2 (LRRK2) is the gene most frequently mutated in familial Parkinson's disease (PD); seven coding mutations characterized by population-specific penetrance (N1437H, R1441G, R1441C, R1441H, Y1699C, G2019S and I2020T) are cause of dominant, late-onset PD [1], while coding and noncoding polymorphisms in the LRRK2 locus are associated with an increased risk of sporadic disease [2]. The gene discussed is LRRK2; the disease is Parkinson disease.