For example, a 2-kb deletion located upstream of the IRGM (immunity related GTPase M) gene is linked with Crohn’s disease [5], a CNV located within the TSPAN8 (tetraspanin 8) gene is associated with type 2 diabetes [6], and a duplication within the CCL3L1 (C–C motif chemokine ligand 3 like 1) gene is involved in HIV susceptibility [7]. Here, IRGM is linked to Crohn disease.