National Registry of IRPF in China

Inclusion Criteria: * Conforming to the diagnostic criteria of IRPF;Definite IRPF must have the following characteristics: (1) The typical finding of Imaging shows retroperitoneal mass, surrounding the abdominal aorta and iliac arteries, with encasement of ureters and/or organ dysfunction; (2) Exclusion of disease progression after standard glucocorticoid treatment; and (3) histopathological findings shows a fibrous tissue with signs of chronic inflammation. The inflammatory component is comprised of lymphocytes, plasma cells and macrophages. Neutrophils and granulomas are rare findings. Possible IRPF required (1) and (2), but without histopathological examination. Exclusion Criteria: * None of them met the criteria for other autoimmune diseases. None had malignant disease. Secondary forms of RPF related to drugs, infections, malignancies, Erdheim-Chester disease and IgG4-RD, need to be excluded.