Histologic alterations are common in Monogenic Disease patients with 'healthy' endoscopy: Results from a GIPAD-GIPPI multicenter study.

Objective: Very early-onset inflammatory bowel disease (VEO-IBD) is a clinical umbrella term referring to IBD-like symptoms arising in children before 6 years of age, encompassing 'pure' IBD (Crohn's Colitis/Ulcerative Colitis)/non IBD colitis, and monogenic diseases (MDs), the latter often related to primary immunodeficiency disorders. A multidisciplinary approach is imperative for correct therapeutic management, as endoscopy and histology are not always completely informative. In this setting, the study aims to describe the extent/features of histologic lesions in both endoscopically damaged mucosa and otherwise endoscopically healthy (normal/near normal) mucosa.

Methods: Endoscopic data were retrospectively recorded, and histologic slides were collegially re-evaluated in a 93 VEO-IBD multicenter cohort, 76 (76/93 - 81,7 %) of which with complete endoscopic/histologic data.

Results: At endoscopy, lesions were reported by the clinician in 66/76 (86,8 %) cases. When endoscopic lesions were reported, histologic damage was also seen. Interestingly, histologic mucosal damage was also documented in 43,3 % (13/30) of cases with endoscopically healthy/nearly healthy mucosa. This misalignment between endoscopy and pathology was seen in about a third of (29,1 % - 7/24) 'true' IBD and all MDs (100 % - 6/6) (p = 0.0029).

Conclusion: In VEO-IBD, histologic lesions can be present in endoscopically 'healthy' intestinal mucosa. This finding is more frequent in MDs, suggesting the need to accurately sample all the mucosal tract in VEO-IBD patients, even when no endoscopic lesions are seen at endoscopy.