DEFA1 and Cowden disease: Fellermann et al. (2006) showed that healthy volunteers as well as UC patients have 2 to 10 copies of the human beta-defensin 2 (HBD-2) gene with the median of 4 copies. However, patients with colonic CD have lower HBD-2 copy than the controls. In addition, they also found that less than four copies of HBD-2 gene were correlated with diminished mucosal HBD-2 mRNA expression (Fellermann et al., 2006). The DEFA1A3 gene encodes alpha-defensins 1–3. Jespersgaard et al. (2011) found that a higher DEFA1A3 copy number was related to CD, especially to colonic CD.