A Case of IgG4-Related Disease Manifested by a Pseudocyst

To the Editor: IgG4-related disease (IgG4-RD) is a chronic inflammatory and fibrosing disease characterized by tumefactive lesions, dense lymphoplasmacytic infiltrates, and abundant IgG4+ plasma cells in the affected tissues. Common histological features are now known to characterize IgG4-RD in essentially every organ in the body, including the pancreas, hepatobiliary duct, lacrimal and salivary glands, lung, kidney, retroperitoneum, aorta, and lymph nodes. The classic organ involved in IgG4-related disease is the pancreas, which typically presents with sausage-shaped enlargement of the gland with loss of fat clefts.