In 1998, frontotemporal dementia associated with parkinsonism was linked to chromosome 17 (FTDP-17), leading to the discovery of the microtubule-associated protein tau gene (MAPT) [4–6] in 1998 and of the progranulin gene (GRN) in 2006 [7, 8]. Here, GRN is linked to Parkinson disease.