Abstract Objective. The purpose of our study was to determine the number of IgG4-related retroperitoneal fibrosis (RPF) cases that were initially diagnosed as idiopathic RPF and to investigate clinical characteristics of IgG4-related RPF. Methods. We retrospectively reviewed the medical records of 41 RPF patients who were treated at our tertiary care medical center in South Korea between January 2000 and January 2013. We identified cases of 19 patients in which a diagnosis was made based on percutaneous biopsy or surgery and selected these cases for further analysis. Immunostaining for IgG4 and histopathologic examinations were performed for pathology specimens. Results. In the 19 RPF patients, more than 30 IgG4-positive plasma cells per specimen were identified in 9 cases with dense lymphoplasmacytic infiltrates, storiform fibrosis, or obliterative phlebitis (IgG4-related RPF group). The recurrence rate of IgG4-related RPF was significantly higher than that of idiopathic RPF (67% vs. 10%, p = 0.015). Initial and cumulative steroid dosages were not different between the two groups. Conclusions. We found that 47% of the patients initially diagnosed with idiopathic RPF showed IgG4-related RPF evidence according to the pathology and IgG4-related RPF patients showed higher recurrence rate than idiopathic RPF patients. We suggest that maintenance immunosuppressive therapy is required in IgG4-related RPF patients.
Keywords: Idiopathic retroperitoneal fibrosis; IgG4; IgG4-related retroperitoneal fibrosis.