Multicentric Castleman disease involving the bone marrow in an immunocompetent patient masquerading as a non-Hodgkin lymphoma – A diagnostic conundrum

Multicentric Castleman disease (MCD) is a polyclonal hematological disorder characterized by constitutional symptoms, organomegaly, significant lymphadenopathy, cytopenias, and symptoms of hypergammaglobulinemia, attributed to excessive interleukin-6 production. The clinical presentation, as well as the bone marrow features of MCD, is not unique and overlaps with a myriad of diseases such as chronic infections, autoimmune diseases, and hematological neoplasms, creating diagnostic difficulty. In this case report, we describe the bone marrow pathology of MCD diagnosed in an elderly immunocompetent patient who presented with clinical features of non-Hodgkin lymphoma, along with a brief discussion on its differential diagnosis.