[A case of multicentric Castleman disease with massive infiltration of plasmacytes presenting IgG4].

A 42-year-old Japanese woman was referred to our university hospital due to progressive anemia and bilateral hilar lymphadenopathy with diffuse ground-glass attenuation on chest computed tomography in December 2009. She had suffered from exertional dyspnea and fatigue for several months. Laboratory findings on admission demonstrated leukocytosis (10,950/ul), elevation of C-reactive protein (4.7 mg/dl), IL-6 (19.9 pg/ml), IgG4 (567 mg/dl) and polyclonal hyper gamma-globulinemia. Chest computed tomography represented mediastinal and bilateral hilar lymphadenopathy with diffuse centrilobular fine nodules and intralobular septal thickening. Histopathological findings of the specimens obtained by thoracoscopic lung and mediastinal lymph node biopsies revealed massive infiltration of IgG4-positive plasma cells in lung tissue and lymph nodes. Pathological findings and high levels of C-reactive protein and interleukin-6 suggested a diagnosis of multicentric Castleman's disease (MCD). In addition, pathological findings of peribronchiolar infiltration of IgG4-positive plasma cells and lymphoid follicles with infiltration of IgG4-positive plasma cells with a high level of IgG4 were indicative of the complication of IgG4-related lung disease. Radiological and serological findings improved rapidly soon after the initiation of oral corticosteroid treatment. It was speculated that this case indicated the close relationship between MCD and IgG4-related lung disease.