[IgG4-related disease, the new "great mimicker": report of one case].

Due to its multisystem involvement, IgG4 -related disease should be considered in the differential diagnosis of medical conditions such as lymphadenopathies, aortitis, serositis and retroperitoneal fibrosis. It shares features with other entities historically described as "great mimickers" such as syphilis, tuberculosis, sarcoidosis, and systemic lupus erythematosus. We report a 40 year-old male with recurrent effusive - constrictive pericarditis, lymphadenopathy and aortitis. The study revealed an inactive tuberculosis with negative cultures for acid fast bacilli. The patient had high serum levels of IgG4 and a mediastinal lymph node biopsy was consistent with IgG4 -related disease. The patient was treated with prednisone 40 mg/day with an excellent response.