IgG4-related sclerosing disease is characterized by infiltration of various tissues and organs, including lung, kidney, pancreas, salivary glands, biliary tree, breast and vessels with IgG4-rich plasma cells. Fibroinflammatory infiltration of these tissues usually progress into fibrosis, eventually resulting in organ failure. In this case report, ultrasonography, computed tomography and positron emission computed tomography features of IgG4-related sclerosing disease involving the retroperitoneum and mesentery are presented together with histopathologic correlation. (C) 2017 The Egyptian Society of Radiology and Nuclear Medicine. Production and hosting by Elsevier.