Transient Pleural Fluid Infiltration by Clonal Plasma Cells Associated with Pulmonary Tuberculosis

Pleural effusion is a rare presentation of plasma cell myeloma, occurring in around 6% of patients during the course of their disease, most commonly as a consequence of a concurrent disease process like heart failure secondary to amyloid deposition. Direct infiltration of the pleural fluid by malignant cells leading to myelomatous pleural effusion is a rare mechanism occurring in less than 1% of patients with plasma cell myeloma, and it is associated with a worse prognosis. There are few case reports of myelomatous pleural effusion as an initial presentation of multiple myeloma. Pleural fluid infiltration by monoclonal plasma cells in the absence of an underlying plasma cell myeloma was not reported before in the literature. Tuberculosis is a known cause of polyclonal gammaglobulinemia, however few case reports described the coexistence of monoclonal gammopathy of undetermined significance and tuberculosis. Here we present an interesting case of pleural fluid infiltration by an abnormal looking clonal plasma cells associated with active pulmonary tuberculosis and parapneumonic effusion in a patient with a background of acute myeloid leukemia. Interestingly, the clonal plasma cell proliferation was confined to the pleural fluid without any evidence of an underlying plasma cell neoplasms (including monoclonal gammopathy of undetermined significance and plasmacytomas). Since our patient had an underlying meyloid neoplasm, we though about the possibility of secondary malignancy. However, in almost all patients with coexisting myeloid and plasma cell neoplasms, myeloid neoplasms developed following chemotherapeutic treatment of plasma cell neoplasms not the other way around. Given that, one must conclude localized extramedullary (pleural) plasma cell proliferation probably represents a transient reactive process to pulmonary tuberculosis which is an extremely rare phenomenon and not described before.