Pleural effusion related to IgG4

Abstract

Purpose of review: The causes of exudative pleural effusions are diverse and frequently remain unclear despite exhaustive examinations. Recently recognized IgG4-related disease (IgG4-RD) is a fibroinflammatory disorder that can affect nearly any organ including the lungs. This review will focus on the involvement of IgG4 in exudative pleural effusion of unknown cause.

Recent findings: IgG4 is found to be involved in a proportion of patients with undiagnosed pleural effusions. Pleural involvement in IgG4-RD can be seen in isolation or association with other organ disease. Pleural thickening and/or effusion are common clinical features of IgG4-related pleural lesions, and this condition is histologically characterized by a lymphoplasmacytic infiltrate enriched in IgG4-positive plasma cells in the pleura. Although the pathogenesis of IgG4-RD is poorly understood, there is a growing body of evidence that indicates an antigen-driven process requiring T-cell and B-cell interaction in which autoantibodies, plasmablasts, follicular helper T cells and CD4+ cytotoxic T lymphocytes participate.

Summary: The possibility of IgG4-related pleural lesion should be considered in patients with pleural effusion of unexplained cause when lymphoplasmacytic infiltration is seen in a pleural biopsy specimen. This condition is responsive to systemic steroid therapy.

Box 1

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FIGURE 1

(a) Chest radiographs of IgG4-related disease with bilateral pleural effusions in a 75-year-old man. Before (left) and 2 months after the steroid therapy at prednisolone 25 mg/day (right). (b) Chest computed tomography scan of the same patient before the steroid therapy. No specific finding is seen except pleural effusion.

FIGURE 2

Histopathological features of the parietal pleura (a–c) and pleural fluid cell block preparation (d–f) of the patient in Fig. 1. Hematoxylin and eosin staining (a and d), Immunostaining for IgG (b and e) or IgG4 (c and f), (a–c) magnification × 200. (d–f) magnification × 400. Diffuse sclerosing inflammation with lymphoplasmacytic infiltration, but no malignant cells, was identified. Fibrosis was pronounced on the side of the pleural cavity (a–c, top). The cell block was prepared at the time of relapse of pleural effusion. The parietal pleura and the pleural fluid cell block reveal the abundance of IgG4-positive plasma cells and a high IgG4/IgG-positive plasma cell ratio.