Sclerosing mesenteritis: A real manifestation or histological mimic of IgG4-related disease?

We present three cases of sclerosing mesenteritis and review the literature to learn whether or not sclerosing mesenteritis is an IgG4-related disease (IgG4-RD). Our patients were all adult males. Their mesenteric masses ranged from 6.5 to 14.5 cm in the greatest diameter. Tissue specimens showed moderate to severe lymphoplasmacytic infiltration with occasional eosinophils against a background of irregular fibrosis. Both obliterative phlebitis and storiform fibrosis were noted in all cases. IgG4+ plasma cells were moderately increased in number (46 to 85 cells/high-power field). However, unlike IgG4-RD, the IgG4+/IgG+ plasma cell ratio was <40% (28% to 35%). Serum IgG4 concentrations were also within the normal range (43.2 to 105 mg/dL; normal range <135 mg/dL). Two biopsy cases showed spontaneous regression on imaging approximately 5 months later. No sclerosing conditions were found in other organs. The literature review identified 11 additional cases of sclerosing mesenteritis with IgG4+ plasma cell infiltration. However, conclusive cases with four characteristic features (high serum IgG4 levels, tissue IgG4 elevation, multi-organ involvement, and effective response to glucocorticoid therapy) have never been reported. In conclusion, although sclerosing mesenteritis shares histological features with IgG4-RD, most cases are less likely to be IgG4-related. IgG4-RD seemingly seldom, if ever, affects this anatomical site.