Over 90 risk variants have been identified in genome-wide association studies (GWAS), and common genetic variants such as Nucleotide-bling oligomerization domain2 (NOD2), leucine-rich repeat kinase 2 (LRRK2), and microtubule-associated protein tau (MAPT) genes have been found between PD and CD [7,20]. Here, LRRK2 is linked to Parkinson disease.