ABSTRACT
Multiple myeloma (MM) is a malignant disease of plasma cells in the bone marrow and forms part of a spectrum of plasma cell disorders that also includes monoclonal gammopathy of undetermined significance (MGUS), solitary plasmacytomas (bone or extramedullary) and primary amyloidosis. Myeloma is characterized by the production of a monoclonal immunoglobulin (Ig) molecule and is associated with clinical symptoms relating to bone destruction, disturbed bone marrow function, reduction of normal immune function and renal failure. In 80 per cent of patients there is a paraprotein in the serum, usually of IgG or IgA subtype. The abnormal cells may also produce free light chains, which pass into the urine as Bence Jones protein (BJP), frequently causing tubular damage. In 20 per cent of patients, free light chains only are produced (Bence Jones only myeloma) and there is no paraprotein in the serum. The number of plasma cells in the bone marrow is increased and osteoclasts are activated in the region of plasma cell foci, causing bone resorption. The residual normal B-cell population is suppressed, leading to a reduction in polyclonal immunoglobulins (immune paresis) and increased susceptibility to infection. The median survival is 3-4 years, although survival varies widely according to a number of prognostic factors.
