CLDN2 and Crohn disease: Moreover, in Crohn’s disease patients, the impairment of epithelial junctional complexes was found to significantly contribute to the development of chronic inflammatory conditions, which may be caused by an increased expression of claudin-2 (CLDN2) and an impaired expression and redistribution of claudin-5 (CLDN5), claudin-8 (CLDN8) and occludin (OCLN).