Fibrinogen/fibrin deposits in mesenteric lymphadenitis due to Yersinia pseudotuberculosis type I: morphologic, immunohistochemical and electron microscopic studies of one case.

A case of mesenteric lymphadenitis due to Yersinia pseudotuberculosis type I is described in a young adult. The diagnosis is suggested by histological appearance and confirmed by serological tests. Histological and semithin sections reveal granulomas with central microabscesses and concentric coagulative necrosis. By histochemical and immunohistochemical techniques, fibrinogen/fibrin deposits are observed as a prominent intercellular meshwork around microabscesses or as loosely intertwining strands in small granulomas. Electron microscopy shows fibrinogen/fibrin deposits closely associated both fibrous long-spacing (FLS) fibers and thin collagen fibers. The pathogenesis and type of granuloma as well as the significance of fibrinogen/fibrin deposits are discussed with reference to current literature.