CASE PRESENTATION: A 53 year-old female house keeper, with a history of intermittent cough and progressive exertional dyspnea of 10-year duration, was admitted for worsening dyspnea and chest tightness. She was diagnosed as “sarcoidosis” in 2002 by the pathological findings of mediastinal lymph nodes obtained using mediastinoscopy. Low dose prednisolone and intermittent cyclophosphamide were administrated since then. However, her clinical symptoms gradually improved. She needed a long term oxygen therapy to maintain her basic activities of daily living. Chest CT taken at admission revealed mediastinal and hilar adenopathy, companied with diffused pulmonary parenchymal infiltration and multiple small thin walled cysts. Lab result revealed polyclonal hyperglobulinemia, elevated erythrocyte sedimentation rate and mild anemia. Lung function test showed both obstructive and restrictive ventilator abnormalities. video-assisted thoracoscopic lung biopsy was done to explore the etiology. Histopathology and immunohistochemistry of the specimens revealed hyperplasia of the lymphoid follicles with germinal centers, plasma cell infiltration which stained positively with either anti-kappa chain or anti-lambda chain antibodies. A diagnosis of multicentric Castleman disease was finally made.