LRRK2 and Parkinson disease: Approximately 5–10% of PD patients have a family history associated with certain gene mutations (LRRK2, PARK7, PINK1, Parkin RBR E3 Ubiquitin Protein Ligase [PRKN], and SNCA), while the majority of cases (90–95%) are sporadic and potentially linked to environmental toxin exposure (pesticides, heavy metals, organic solvents).