LRRK2 and Parkinson disease: Interestingly, genome-wide association studies have identified that LRRK2 gene is also a common susceptibility locus for Crohn’s disease (CD), a chronic inflammatory disease of the GI tract.15,16 Moreover, several epidemiological studies have shown that patients with CD had an increased risk of PD, and had higher levels of LRRK2 in inflamed colonic tissue.17,18 In addition, individuals carrying LRRK2 risk variants were highly susceptible to GI disturbances, mainly constipation.19