The peak in our SPL + MPL GWAS was at rs382259 in the MHC class III region, near NOTCH4. This overlaps with a GWAS signal for Crohn’s disease (P = 1.4 × 10−9, OR = 2.3), as well as a secondary signal for ulcerative colitis chr6: 32,280,470–32,282,252 (IMAGEN et al., 2009). Here, NOTCH4 is linked to Crohn disease.