About 30% of the familial and 3–5% of the sporadic PD cases are monogenic forms that derive from a single mutation in a gene and that can be inherited dominantly, such as SNCA (PARK1 = 4), and LRRK2 (PARK8) or recessively, such as Parkin (PARK2), PINK1 (PARK6), DJ-1 (PARK7), and ATP13A2 (PARK9) [46]. The gene discussed is LRRK2; the disease is Parkinson disease.