SMAD3 and Crohn disease: Functional gastrointestinal disorders (FGID) studies have shown that genes related to asthma, such as DENND1B, SMAD3, SLC22A4/5 (5q31/IBD5), and ORMDL3, have been co-associated with Crohn's disease and ulcerative colitis (Lees et al. 2011).