CT imaging of IgG4-related retroperitoneal fibrosis showing a soft tissue mass encasing the aorta
CT imaging of IgG4-related retroperitoneal fibrosis showing a soft tissue mass in the renal hilus
FDG-PET/CT showing uptake of FDG around the aorta
The retroperitoneum is also a site where tumor lesions such as malignant lymphoma, desmoid fibromatosis, and liposarcoma often develop . Histological investigation of the retroperitoneal mass is necessary to differentiate IgG4-RF from malignancy with atypical imaging or normal IgG4 levels.
IgG4-RF responds well to steroids, and steroid therapy has become a standard therapy for IgG4-RF [25, 26]. Although a few asymptomatic patients might need only monitoring, steroid therapy is necessary for patients with clinical symptoms or those with hydronephrosis. Zen et al. reported that steroid therapy was effective regardless of the presence/absence of IgG4-related disease or serum IgG4 levels . The starting dose of steroid is usually 30–40 mg/day (0.6 mg/kg/day). The response to steroid therapy is generally favorable except in a few cases .
The long-term prognosis of IgG4-RF is unknown.
Recognition of the concept of IgG4-RF has resulted in great progress in the diagnosis and therapy of RF. The diagnostic criteria for IgG4-RF described herein may be helpful in diagnosing this disease correctly.
This study was partially supported by the Intractable Disease, supported by the Ministry of Health, Labour, and Welfare of Japan.
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