The major causes of renal insufficiency, present initially in half of the patients with multiple myeloma, are "myeloma kidney" and hypercalcemia. There is no reliable evidence that the isoelectric point (pI) or the type of light chain has an important role in renal failure. Acute renal failure must be treated vigorously with appropriate fluids and electrolytes as well as hemodialysis if necessary. The benefit of plasma exchange has not been proven. Primary systemic amyloidosis or light-chain deposition disease is the usual cause of the nephrotic syndrome in patients with monoclonal gammopathy. The monoclonal gammopathies are a group of disorders that are characterized by the proliferation of plasma cells producing a homogeneous, monoclonal protein (M-protein).