Studies from the Polish population have shown that four monogenic genes are involved in the PD pathological process, including parkin RBR E3 ubiquitin protein ligase (PRKN), phosphatase and tensin homolog-induced putative kinase 1 (PINK1), Leucine Rich Repeat Kinase 2 (LRRK2) and α synuclein (SNCA). This evidence concerns the gene LRRK2 and Parkinson disease.