LRRK2 and Parkinson disease: Twenty-three studies with keywords including “DBS,” “apomorphine,” “levodopa carbidopa intestinal gel,” “PD,” “genetic,” and genes including leucine-rich repeat kinase-2 (LRRK2), SNCA, PRKN, PINK1, and Glucocerebrosidase (GBA) were identified from PubMed search.