LRRK2 and Parkinson disease: Mutations that increase the activity of leucine-rich repeat kinase 2 (LRRK2) are a major cause of familial Parkinson’s disease, and common LRRK2 variants also elevate risk for sporadic Parkinson’s disease (Alessi & Pfeffer, 2024; Bentley-DeSousa, Clegg, et al., 2025; Paisan-Ruiz et al., 2004; Rocha et al., 2022; Zimprich et al., 2004).