A Case of Plasmablastic Multiple Myeloma With Extramedullary Disease Manifesting as a Myelomatous Pleural Effusion

Multiple myeloma (MM) is a neoplasm of plasma cell origin characterized by the proliferation of immunoglobulin-producing plasma cells in the bone marrow. Extramedullary disease (EMD) occurs in approximately 10% of patients with MM. Myelomatous pleural effusion (MPE) is a possible manifestation of EMD and has been associated with a poorer prognosis. A 66-year-old female was evaluated after an abnormal serum protein electrophoresis that showed a 2.1 g/dL M-spike in the gamma region, highly suggestive of plasma cell dyscrasia. Imaging subsequently confirmed the bony metastasis. A bone marrow biopsy confirmed plasmablastic MM, and she was started on chemotherapy. She presented three months later with bilateral pleural effusions, with cytology revealing neoplastic plasmacytoid cells. Despite transitioning to dexamethasone, cyclophosphamide, etoposide, and cisplatin (the V-DCEP regimen) due to disease progression, her myeloma remained refractory to treatment, and she expired one month later.