Pararenal retroperitoneal Castleman's disease mimicking systemic lupus erythematosus.

A 41-year-old man diagnosed initially as probable systemic lupus erythematosus (SLE) visited our hospital complaining of a persistent painful oral ulcer and multiple spots like coffee beans on his trunk. Antibodies except for anti-dsDNA and anti-histone antibodies and other serologies were negative. Conventional cytotoxic and immunomodulatory agents did not have any effect on these lesions. Computed tomography for evaluating persistent dry cough incidentally showed a huge mass in the left mid-retroperitoneum. Surgical treatment was done and the final diagnosis was Castleman's disease (CD). CD is a relatively rare disorder characterized by a massive non-malignant tumor of lymphoid tissues, with unknown etiology. It commonly presents as a localized soft tissue mass within the mediastinum or neck, and rarely in the retroperitoneal space. Since some cases of CD may share systemic, immune and histopathologic features of autoimmune disease, exact diagnosis is difficult to make based on the clinical and laboratory clues alone. We report herein an unusual case with pararenal retroperitoneal CD mimicking SLE.