[Two cases of IgG4-related disease with pleural effusion].

We describe 2 cases of IgG4-related disease with pleural effusion in elderly men. Both patients had elevated serum IgG4 levels, and the characteristics of their pleural effusion were similar. Patient 1 had pericardial effusion and retroperitoneal fibrosis, and a biopsy specimen from the pericardium showed infiltration of abundant IgG4-positive plasma cells with fibrosis. Because his pleurisy, pericarditis and retroperitoneal fibrosis responded to steroid therapy, we diagnosed pleurisy associated with IgG4-related disease. Patient 2 had been treated with steroids because of IgG4-related sialadenitis and interstitial pneumonitis, but pleural effusion developed. Although histopathological examination of the pleura showed infiltration of abundant IgG4-positive plasma cells with fibrosis, Mycobacterium tuberculosis was cultured from the pleural effusion, and histologic examination also showed epithelioid granuloma. Chemotherapy for tuberculosis was effective for the pleurisy, and we diagnosed tuberculous pleurisy as a complication of IgG4-related disease. In cases of IgG4-related disease associated with pleural effusion, the clinical course should be considered together with the serum IgG4 levels and pleural histology.