IgG4-related disease involving polyserous effusions with elevated serum interleukin-6 levels: a case report and literature review.

Immunoglobulin G4-related disease (IgG4-RD) is a recently described immune-mediated fibroinflammatory disease with a characteristic histopathologic appearance that can affect various organs. We report a 43-year-old Chinese female patient with IgG4-RD involving polyserous effusions with reports of worsening exertional dyspnea for 3 months. Laboratory blood tests revealed that serum interleukin (IL)-6, carbohydrate antigens (CA-199 and CA-125), and alpha-fetoprotein levels were significantly increased, but serum IgG4 levels were normal. Repeat pleural effusion and ascite analysis showed lymphocyte-predominant exudates. In addition, computed tomography scan showed massive pleural effusion in the right pleural cavity, abdominal effusion, and some pericardial effusion with a partial compression atelectasis. Further, medical thoracoscopy was performed to examine the pleural cavity and found multiple nodules on the pleura and partly thickened pleura with a reddish color. Histopathologic and immunohistochemical examination revealed marked lymphocytes and IgG4-positive plasma cell infiltration. The patient was finally diagnosed with IgG4-RD according to the comprehensive diagnostic criteria, although the patient presented similar serological and pathological manifestations of Castleman disease (CD). Our case suggests that IgG4-RD may be one of the causes of polyserous effusions and shows the difficulties in differentiating between IgG4-RD and CD.