While most casesof PD are sporadic, genetic factors contribute to disease susceptibilityand may interact with environmental exposures.26−28 Mutations ingenes such as SNCA (α-synuclein), LRRK2 (leucine-rich repeatkinase 2), Parkin, PINK1, and DJ-1 are associated with familial formsof PD, providing insights into disease mechanisms. Here, LRRK2 is linked to Parkinson disease.