LRRK2 and Parkinson disease: The LRRK2 p.G2019S (NM_198578.4 (LRRK2): c.6055G > A) variant is estimated to occur in approximately 1% of patients with sporadic PD and 3–6% of patients with familial PD in the United States; it shows the highest penetrance of all reported LRRK2 risk variants (Table 1).