Detection of Eosinophilic Cell-free Granules Based on Expression of CCR3 and MBP Markers in Colonic Biopsy of Pediatric Patients with Suspected and Confirmed Eosinophilic Colitis.

Background: Eosinophilic colitis (EC) is a rare eosinophilic gastrointestinal disorder with increasing frequency in recent years. Although normal eosinophil density varies substantially by colonic segment, several proposed eosinophil thresholds have been used in the literature to support the diagnosis in the appropriate clinical context. However, some patients with clinical features suggestive of eosinophilic colitis (EC) do not demonstrate increased tissue eosinophil counts on histopathologic examination. Objective: To compare eosinophil-derived cell-free granules based on expression of their surface markers between two groups of patients with symptoms consistent with EC: those with increased tissue eosinophils and those without tissue eosinophilia. Methods: This study included 10 pediatric patients with histologically confirmed EC and 13 patients with clinical suspicion of EC. Eosinophil-derived cell-free granules were evaluated in colonic tissue samples using immunohistochemistry (IHC), with antibodies against MBP and CCR3. Results: Eosinophil-derived cell-free granules were detected in all specimens from patients with suspected EC and in the majority of specimens from patients with confirmed EC. Degranulating eosinophils were identified in all specimens from both groups, although the proportion of degranulating eosinophils varied among patients. Furthermore, the abundance of granules was significantly associated with the percentage of degranulating eosinophils. Conclusion: Our findings indicate that IHC can be used to detect eosinophil-derived granules in colonic tissue. The presence of cell-free eosinophil granules with varying abundance, along with evidence of eosinophil degranulation in all specimens from patients with suspected EC, may provide supportive histopathological features that contribute to improving the diagnostic assessment of EC.