In addition, the levels of GDNF present in the intestinal tissues of CD patients were reported to be lower compared to non-IBD controls [35].A recent study has shown that GDNF prevents the degranulation of mast cells in the colon of dextran sulfate sodium-induced colitis in rats, and at the same time, it results in decreased production of pro-inflammatory cytokines in an in vitro cell model of RBL-2H3 cells and rats [38].These observations from cell models are opposite to what we observed in human biopsies ex vivo. Here, GDNF is linked to Cowden disease.