Plasma cell interstitial pneumonia as a manifestation of multicentric Castleman's disease

A 12-year-old boy was admitted to our hospital because of abnormal shadows on a chest radiograph, slight fever, and superficial lymphadenopathy. Laboratory examination showed anemia (Hb 9.9 g/dl) and hyperimmunoglobulinemia (IgG 5469 mg/dl) without M protein. A chest CT scan showed bilateral diffuse shadows and bilateral hilar lymphadenopathy. Biopsy specimens of an inguinal lymph node and a lung showed many lymphoid follicles with germinal centers, and marked infiltration of mature plasma cells in the interfollicular area without destruction of follicular structures. The polyclonality of the plasma cells was confirmed by immunohistochemistry. The patient was not treated because these results excluded malignant disease and he was asymptomatic. At the age of 17 years, he was admitted to our hospital again because of dyspnea and a tendency to bleed. Interstitial pneumonia, hyperimmunoglobulinemia (IgG 13900 mg/dl), and anemia (Hb 6.6 g/dl) were found, along with thrombocytopenia (2.5 x 10(4)/mm3) and proteinuria. The serum interleukin-6 level was high: 177 pg/ml. Bronchoalveolar lavage fluid contained many plasma cells. Therapy with corticosteroids and immunosuppressant medication was effective. Our diagnosis was plasma cell interstitial pneumonia as a manifestation of multicentric Castleman's disease.