NOD2 and inflammatory bowel disease: For example, in monozygotic twin studies, it has been identified that phenotypic concordance is only 50%-70% in CD and 10%-20% in UC.9 Only 2%-14% of the IBD patients have a family history of IBD.10 The first genetic locus on chromosome 16 has been described in 1996 as the first IBD-associated gene locus.11 This locus was characterized as the NOD-2 locus later on.