A Case of Rare Subtype of Multiple Myeloma: Secondary Plasma Cell Leukemia

Description Plasma cell leukemia is a rare, aggressive form of multiple myeloma with the presence of circulating plasma cells in the peripheral blood. There are two types of plasma cell leukemia, primary and secondary, depending on if there was previous evidence of multiple myeloma. The diagnostic criterion of plasma cell leukemia is based on a percentage (>20%) or an absolute number of (≥2 × 10⁹/L) plasma cells in the peripheral circulation. We present the clinical course of a rare case of secondary plasma cell leukemia in a patient from the time of initial diagnosis of multiple myeloma, its remission period of about 5 years, and its final progression into refractory secondary plasma cell leukemia. This case report details the patient's presenting symptoms, pertinent laboratory and diagnostic imaging findings, and histopathology of peripheral blood and bone marrow. This case report presents a chronological comparison of key laboratory findings that manifest the progression of multiple myeloma into secondary plasma cell leukemia. It also offers a brief review of the literature for the diagnosis and treatment of plasma cell leukemia.