Collagenous Gastritis in Primary Selective IgM Deficiency:Transition to EBV+Gastric Adenocarcinoma

SelectiveIgMdeficiency(SIgMD)andisolatedcollagenousgastritisaretwoindependentraredisorders.Ourpurposeistoreportthe 1stcaseofSIgMDandisolatedcollagenousgastritisandcollagenousgastritisthathastransitionedtoEBV+gastricadenocarcinoma.GastricbiopsytissuewasanalyzedbyEBV-relatedencodedRNAinsituhybridizationassay.SubsetsofCD4,CD8,Tfollicularhelpercells(TFH),andmembersofthe“regulatorylymphocytesclub”weremeasuredwithmultiplepanelsofmonoclonalantibodiesandisotypecontrolsbymulticolor flow cytometry. )e patient was diagnosed with SIgMD (extremely low serum IgM 9mg/dl and normal IgG and IgA andexclusion of secondary causes of low IgM). Soon after SIgMD diagnosis, the patient developed collagenous gastritis and, 8 years later,developedgastricadenocarcinomathatwaspositiveforEBV.Anextensiveimmunologicalanalysisrevealedreducedna ̈ıveCD4andCD8effector memory T cells and increased na ̈ıve and central memory CD8 T cells. Among the circulating follicular helper T cells(cTFH),TFH1andTFH2wereincreasedwhereasTFH17wasdecreased.CD4TregcellsandTFRcellswereincreased,whereasBregandCD8Treg were comparable to control. In conclusion, SIgMD may be associated with isolated collagenous gastritis, and collagenous gastritismay transition to EBV+gastric adenocarcinoma. A role of regulatory lymphocytes in gastric cancer is discussed.