Introduction Multiple myeloma is cancer of monoclonal plasma cells produces large amounts of IgG (55%) or IgA (25%) high levels of IL-6 may be present Epidemiology most common primary tumor arising within bone in the elderly If asymptomatic called monoclonal gammopathy of undetermined significance (MGUS) increased gamma globulin on serum electrophoresis but no symptoms of multiple myeloma are present Pathophysiology initial event - abnormal response of B lymphocyte to antigenic stimulation results in monoclonal proliferation of plasma cells -> MGUS additional mutations causes progression from MGUS to multiple myeloma since the plasma cell population in multiple myeloma are clones, they produce the same antibody, resulting in the monoclonal M spike on serum protein electrophoresis though total serum antibody levels increase, these antibodies do not provide protection against pathogens because there is a lack of antibody antigenic diversity Presentation Symptoms bone pain sequelae associated with hypercalcemia sequelae associated with renal failure Evaluation Serum protein electrophoresis monoclonal immunoglobulin spike (M protein) Urinalysis Ig light chains (Bence Jones protein) Peripheral blood smear Russell bodies Ig containing inclusion bodies seen in plasma cells RBC rouleaux formation Igs coat RBC and neutralize the ionic charge than normally repels RBCs Bone marrow aspiration proliferation of large monoclonal plasma cells "fried-egg" appearance Serology hypercalcemia result of bone degradation due to cytokine production that activates RANK receptor on osteoclasts associated with decreased phosphate, increased PTH-rp and decreased vitamin D levels prolonged bleeding time Imaging punched-out lytic bone lesions on x-ray Prognosis, Prevention, and Complications May lead to renal insufficiency ↑ susceptibility to infection anemia primary amyloidosis (AL) Poor prognosis