Gastrointestinal IgG_4 Deposition Is a New Histopathological Feature of Eosinophilic Gastroenteritis

The pathogenesis of eosinophilic esophagitis involves immunoglobulin G4 (IgG4) deposition. However, the relationship between IgG4 and eosinophilic gastroenteritis (EGE) is unclear. To investigate gastrointestinal deposition of IgG4 in EGE. Biopsies of the esophagus, stomach, and small intestine were evaluated in patients with and without EGE. Immunohistochemical staining for IgG4 was performed, and the proportions of the stained areas were compared. Sera from patients with EGE were assayed for food-specific IgG4, including egg white, wheat, rice, soy, and cow milk. Seventeen patients were included in this study (EGE group, n = 10; control group, n = 7). Compared with the control group, the proportion of IgG4-stained area in the EGE group was approximately threefold higher (40.2% [32.3–49.5]) vs. 12.1% [4.0–21.9], p = 0.014) in the esophagus, fivefold higher in the stomach (17.3% [11.1–26.2] vs. 3.7% [1.5–5.2], p = 0.014), and sixfold higher in the small intestine (28.0% [15.0–33.2] vs. 4.5% [2.6–9.8], p = 0.019). There was no significant association between the proportion of IgG4-stained area and the number of infiltrating eosinophils. Serum egg white-specific IgG4 levels were correlated with the proportion of IgG4-stained areas in the small intestine (R = 0.7, p = 0.035). IgG4 accumulated within the gastrointestinal mucosa in EGE. The positive correlation between serum egg white-specific IgG4 levels and the proportion of IgG4-stained areas in the small intestine suggests a role for IgG4 in the disease pathophysiology.