While the clinical presentation of motor symptoms of LRRK2 parkinsonism has been largely indistinguishable from sporadic PD, there is a striking difference in the age at onset (AAO), disease penetrance, and neuropathological features, ranging from nigrostriatal loss with inconsistent occurrences of Lewy body (LB) and Alzheimer’s pathology, lack thereof, or atypical neuropathology. This evidence concerns the gene LRRK2 and Parkinson disease.