In addition to overlapping clinical and neuropathological features, rare, highly penetrant pathogenic variants in SNCA (α-synuclein) [43, 68, 92] and LRRK2 (leucine-rich repeat kinase 2) [65, 94] have been identified in patients with phenotypes ranging from familial PD to DLB. Here, LRRK2 is linked to Parkinson disease.