Idiopathic multicentric Castleman disease complicated by unilateral pleural thickening and massive pleural effusion: A case report

Idiopathic multicentric Castleman disease (iMCD) is a benign lymphoproliferative disease characterized by generalized lymphadenopathy and systemic inflammatory symptoms, occurring in individuals without infection with human immunodeficiency virus (HIV) or Kaposi sarcoma–associated herpesvirus (KSHV). iMCD is typically subclassified into iMCD-TAFRO, which is characterized by thrombocytopenia, ascites, fever, reticulin fibrosis, and organomegaly; iMCD with idiopathic plasmacytic lymphadenopathy (iMCD-IPL), which follows a chronic disease course with persistent lymphadenopathy, marked polyclonal hypergammaglobulinemia, and prominent plasma cell infiltration in lymph nodes; and iMCD–not otherwise specified (iMCD-NOS), which lacks features of both TAFRO syndrome and the IPL phenotype. Pleural thickening and effusion are extremely rare manifestations of iMCD-NOS. Herein, we present a rare case of iMCD-NOS presenting with unilateral pleural thickening and pleural effusion. A 76-year-old Japanese man was referred for further evaluation of a massive left-sided pleural effusion with tracheal compression. Fluorodeoxyglucose positron emission tomography/computed tomography showed increased uptake in the thickened pleura and multiple lymph nodes. Histopathological examination of a mediastinal lymph node demonstrated medullary and lymphoid follicular hyperplasia without structural destruction, while biopsy of the thickened pleura showed infiltration of lymphocytes and plasma cells without dysplasia. The patient was treated with corticosteroids and tocilizumab, resulting in marked improvement in symptoms and pleural effusion. This case highlights the importance of considering pleural and lymph node biopsies for accurate diagnosis and of not excluding iMCD in patients with unilateral pleural thickening accompanied by multiple lymphadenopathies.