To summarize, the strongest genetic associations have been observed in IBDs for the interleukin-24 receptor (IL-23R) gene, in CD for nucleotide-binding oligomerization domain-containing protein 2/caspase recruitment domain family member 15 (NOD2/CARD15) gene, and in UC for the human leukocyte (HLA) complex [98,100]. Here, NOD2 is linked to Cowden disease.