Multiple myeloma natural history

Natural History
Because many organs can be affected by myeloma, the symptoms and signs vary greatly. A mnemonic sometimes used to remember the common tetrad of multiple myeloma is CRAB - C = Calcium (elevated), R =Renal failure, A = Anemia, B = Bone lesions. Myeloma has many possible symptoms, and all symptoms may be due to other causes. They are presented here in decreasing order of incidence.

Myeloma bone pain usually involves the spine and ribs, and worsens with activity. Persistent localized pain may indicate a pathological bone fracture. Involvement of the vertebrae may lead to spinal cord compression. Myeloma bone disease is due to proliferation of tumor cells and release of IL-6, also known as osteoclast activating factor (OAF), which stimulates osteoclasts to break down bone. These bone lesions are lytic in nature and are best seen in plain radiographs, which may show a "punched-out" resorptive lesions. The breakdown of bone also leads to release of calcium into the blood, leading to hypercalcemia and its associated symptoms.
 * Bone pain

The most common infections are pneumonias and pyelonephritis. Common pneumonia pathogens include S pneumoniae, S aureus, and K pneumoniae, while common pathogens causing pyelonephritis include E coli and other gram-negative organisms. The increased risk of infection is due to immune deficiency resulting from diffuse hypogammaglobulinemia, which is due to decreased production and increased destruction of normal antibodies.
 * Infection

Renal failure may develop both acutely and chronically. It is commonly due to hypercalcemia (see above). It may also be due to tubular damage from excretion of light chains, also called Bence Jones proteins, which can manifest as the Fanconi syndrome (type II renal tubular acidosis). Other causes include glomerular deposition of amyloid, hyperuricemia, recurrent infections (pyelonephritis), and local infiltration of tumor cells.
 * Renal failure

The anemia found in myeloma is usually normocytic and normochromic. It results from the replacement of normal bone marrow by infiltrating tumor cells and inhibition of normal red blood cell production (hematopoiesis) by cytokines.
 * Anemia

Common problems are weakness, confusion and fatigue due to hypercalcemia. Headache, visual changes and retinopathy may be the result of hyperviscosity of the blood depending on the properties of the paraprotein. Finally, there may be radicular pain, loss of bowel or bladder control (due to involvement of spinal cord leading to cord compression) or carpal tunnel syndrome and other neuropathies (due to infiltration of peripheral nerves by amyloid). It may give rise to paraplegia in late presenting cases.
 * Neurological symptoms

Prognosis
The International Staging System can help to predict survival, with a median survival of 62 months for stage 1 disease, 45 months for stage 2 disease, and 29 months for stage 3 disease.

Cytogenetic analysis of myeloma cells may be of prognostic value, with deletion of chromosome 13, non-hyperdiploidy and the balanced translocations t(4;14) and t(14;16) conferring a poorer prognosis. The 11q13 and 6p21 cytogenetic abnormalities are associated with a better prognosis.

Prognostic markers such as these are always generated by retrospective analyses, and it is likely that new treatment developments will improve the outlook for those with traditionally 'poor-risk' disease.