IgG4-related disease–like fibrosis as an indicator of IgG4-related lymphadenopathy

The significance of IgG4-related diseases including IgG4-related lymphadenopathy has recently been recognized worldwide. Inflammatory pseudotumors in lymph nodes, as well as in other organs, are also recognized as IgG4-related diseases. Only a few case reports have described IgG4-related lymphadenopathy with fibrosis (IgG4-fibrosing lymphadenopathy), and IgG4-fibrosing lymphadenopathy has not been compared clinicopathologically with non–IgG4-related lymphadenopathy with fibrosis. We have evaluated the pathologic features in 13 patients with IgG4-fibrosing lymphadenopathy, including IgG4 and IgG expression in lymph nodes, and compared these features with those of patients with non–IgG4-related lymphadenopathy with fibrosis with reactive inguinal lymphadenopathy and focal fibrosis and lymph nodes at least 10 mm in diameter. IgG4-fibrosing lymphadenopathy was characterized by lymphoplasmacytic and eosinophilic infiltration, many IgG4-positive plasma cells in fibrotic areas, and high serum IgG4 concentrations. The IgG4-positive/IgG-positive plasma cell ratio was significantly higher in the IgG4-fibrosing lymphadenopathy than in the non–IgG4-fibrosing lymphadenopathy group. The presence of even minor fibrosis with characteristics of IgG4-related disease such as IgG4-fibrosing lymphadenopathy may facilitate the diagnosis of IgG4-related lymphadenopathy.