LRRK2 and inflammatory bowel disease: The most significant loci identified in genome-wide association studies (GWAS) for IBD include protein-altering alleles in IL23R (interleukin 23 receptor), NOD2 (nucleotide oligomerization domain 2), ATG16L1 (autophagy-related 16-like 1) (Huang et al., 2017), LRRK2 (leucine-rich repeat kinase 2) (Hui et al., 2018) and CSF2RB (colony stimulating factor 2 receptor) (Chuang et al., 2016), as well as non-coding risk alleles near PTGER4 (prostaglandin E receptor 4), that increase gene expression (Libioulle et al., 2007; Jostins et al., 2012; Liu et al., 2015).