A case of IgG4-related sclerosing mesenteritis.

IgG4-related disease has been recognized as a systemic syndrome characterized by mass-forming lesions with lymphoplasmacytic infiltration and sclerosis. This disease has been identified in various sites, including the pancreas, retroperitoneum, lung, head, and neck. Herein we report a case of IgG4-related sclerosing mesenteritis. An 82-year-old woman was admitted to our hospital due to persistent abdominal pain. Abdominal computed tomography demonstrated a solitary mass with a maximal diameter of 11.7cm in mesentrium of the small intestine. On her laboratory examination, only C-reactive protein level was elevated. Although the pre-operative diagnosis was indefinite, she underwent ileocecectomy. Grossly, an elastic soft mass with foci of hemorrhage was seen in the mesentrium. Microscopically, the lesion was composed of fibroblastic or myofibroblastic spindle cells with abundant stromal fibrosis and inflammatory infiltrate, such as lymphocytes and plasma cells accompanied by lymphoid follicles with a germinal center. Obstructive phlebitis was observed. Immunohistochemically, numerous IgG4-positive plasma cells were observed, and the IgG4/IgG ratio was 75.9%. The serum level of IgG4 examined at post-operation was high. These findings suggested that this lesion was consistent with IgG4-related sclerosing mesenteritis.