Russell body gastritis resolved after Helicobacter pylori eradication: a case report and review of the literature.

Russell body gastritis (RBG) is a rare gastric inflammatory lesion characterized by dense infiltration of plasma cells containing Russell bodies (RBs) known as Mott cells. Here, we report a case of RBG that showed resolution 2 months after Helicobacter pylori eradication. A gastric biopsy revealed numerous eosinophilic globular RBs and signet ring cell-like Mott cells. H. pylori infection was identified on the surface of foveolar epithelial cells. Alcian blue staining was negative for RBs. Periodic acid-Schiff staining showed that most RBs were negative, with only a few RBs and Mott cells showing weak positivity. Immunohistochemical staining for immunoglobulin G (IgG), kappa, and lambda light chains was performed on paraffinembedded tissue. Plasma and Mott cells were positive for CD79a, CD138, IgG, kappa, and lambda. However, despite being traditionally considered as aggregates of immunoglobulin molecules, the majority of RBs are negative for IgG and light chain determinants. The marked reduction in RBs and reappearance of normal plasma cells following H. pylori eradication suggest that RB formation is a reversible and reactive process. However, the lack of staining in certain immunohistochemical analyses indicated the presence of unexpected alterations in immunoglobulin composition. The precise biochemical nature and fate of RBs warrant further investigation.