Probing the gut barrier: epithelial permeability as a dynamic marker in eosinophilic gastroenteritis via pCLE

: Eosinophilic gastroenteritis (EGE) is a rare, chronic inflammatory condition characterized by symptoms and eosinophilic infiltration of the gastrointestinal tract in the absence of secondary causes of gastrointestinal eosinophilia. The advent of probe-based confocal laser endomicroscopy (pCLE) has introduced the possibility of real-time, in vivo microscopic imaging, enabling dynamic assessment of mucosal architecture and barrier function. We report the case of a 32-year-old woman with an atypical manifestation of mucosal EGE, initially presenting with pseudothrombotic microangiopathy secondary to vitamin B12 deficiency. The diagnostic work-up included standard endoscopy, histopathological examination of biopsy samples, and pCLE imaging. pCLE was performed both at baseline and during follow-up to evaluate disease distribution and monitor therapeutic response. Imaging was conducted using the GastroFlex UHD Confocal Miniprobe connected to the Cellvizio system, with images captured within 10 min of intravenous fluorescein administration, digitally stored, and later reviewed by blinded pCLE experts. Initial assessment revealed marked eosinophilic infiltration in the stomach, terminal ileum, and cecum, with corresponding interstitial leakage and inflammatory cell infiltration observed on pCLE. Increased epithelial permeability was also detected in additional intestinal segments lacking histological involvement. After 5 weeks of corticosteroid therapy, the patient achieved clinical and histological remission, accompanied by normalization or significant improvement in pCLE findings. Interestingly, pCLE continued to reveal subtle barrier dysfunction in regions showing histological recovery, highlighting persistent subclinical mucosal alterations. This case underscores the value of pCLE in identifying early intestinal barrier dysfunction and in monitoring therapeutic response in EGE. The concordance between pCLE imaging, histological findings, and clinical outcomes supports its use as a complementary diagnostic and monitoring tool in EGE management.