Multiple myeloma is a debilitating malignancy that is part of a spectrum of diseases ranging from monoclonal gammopathy of unknown significance (MGUS) to plasma cell leukemia.Multiple myeloma can cause a wide variety of problems. The proliferation of plasma cells may interfere with the normal production of blood cells, resulting in leukopenia, anemia, and thrombocytopenia. The cells may cause soft-tissue masses (plasmacytomas) or lytic lesions in the skeleton. Feared complications of multiple myeloma are bone pain, hypercalcemia, renal failure, and spinal cord compression.The aberrant antibodies that are produced lead to impaired humoral immunity, and patients have a high prevalence of infection. The overproduction of these antibodies may lead to hyperviscosity, amyloidosis, and renal failure.