Sclerosing Mesenteritis as an Uncommon Site of Involvement of IgG4-Related Disease: A Case Report With an Updated Review of the Literature.

Immunoglobulin G4-related disease (IgG4-RD) is an uncommon immune-mediated disorder most commonly involving the pancreas, lacrimal, and salivary glands. Immunoglobulin G4-related sclerosing mesenteritis (IgG4-RSM) is a rare site of involvement that usually mimics the imaging characteristics of mesenteric malignancies. Herein, we report a case of IgG4-RSM followed by an updated and comprehensive review of the literature. A 73-year-old woman presented with colicky abdominal pain in the right hypochondrium. The findings on contrast medium computed tomography (CMCT) showed a swelling of the mesenteric root with vascular structures surrounded by slightly contrast-impregnated tissue and irregular margins. The 18F-fluorodeoxyglucose positron emission tomography/computed tomography (18F-FDG-PET) showed an area of inhomogeneous and intense hypermetabolism of the mesenteric root. Hence, laparoscopic resection of the mesenteric root was performed to distinguish such masses from malignant tumors, obtaining specimens for histopathologic examination. The latter exhibited tissue infiltration with lymphocytes, IgG4-positive plasma cells, and fibrosis, indicating a diagnosis of IgG4-RSM in the presence of both elevated serum IgG4 levels and the aforementioned imaging findings. With steroid therapy, no clinical signs of re-exacerbation within a one-year follow-up were observed and serum IgG4 levels returned to normality. Aiming to evaluate the real frequency of IgG4-RSM in view of the 2017 Comprehensive Diagnostic Criteria (CDC) of IgG4-RD, we undertook a complete MEDLINE, EMBASE, Web of Science, and Scopus database search of all case reports of IgG4-RSM published so far. Such criteria were met in only six cases with a definite diagnosis. This case highlights the mesentery as a rare site of involvement of IgG-RD and allows us to advance knowledge of IgG4-RSM.