Weidlich S, et al. - In this investigation, researchers compared esophageal immunoglobulin (Ig)G4 plasma cell infiltration and serum IgG4 levels of eosinophilic esophagitis (EoE) patients (before and after budesonide therapy) with gastroesophageal reflux disease (GERD), the most important differential diagnosis of EoE, patients. In total, 14 GERD patients were taken as a control group without histological evidence of eosinophilic infiltration. In EoE patients elevated systemic IgG4 serum levels vs GERD patients can be seen and decrease under topical steroid therapy. Local expression of IgG4 plasma cells is also high in EoE, but not in patients with GERD, and under therapy normalize. These findings are further evidence of a possible association between EoE and IgG4. No relevant esophageal plasma cell infiltration could be seen in GERD patients.