Multiple Myeloma Diagnosis

Investigations

The presence of unexplained anemia, kidney dysfunction, a high erythrocyte sedimentation rate (ESR) and a high serum protein (especially raised immunoglobulin) may prompt further testing. A doctor will request protein electrophoresis of the blood and urine, which might show the presence of a paraprotein (monoclonal protein, or M protein) band, with or without reduction of the other (normal) immunoglobulins (known as immune paresis). One type of paraprotein is the Bence Jones protein which is a urinary paraprotein composed of free light chains (see below). Quantitative measurements of the paraprotein are necessary to establish a diagnosis and to monitor the disease. The paraprotein is an abnormal immunoglobulin produced by the tumor clone. Very rarely, the myeloma is ''nonsecretory'' (not producing immunoglobulins).

In theory, multiple myeloma can produce all classes of immunoglobulin, but IgG paraproteins are most common, followed by IgA and IgM. IgD and IgE myeloma are very rare. In addition, light and or heavy chains (the building blocks of antibodies) may be secreted in isolation: κ- or λ-light chains or any of the five types of heavy chains (α-, γ-, δ-, ε- or μ-heavy chains).

Additional findings include: a raised calcium (when osteoclasts are breaking down bone, releasing calcium into the bloodstream), raised serum creatinine due to reduced renal function, which may be due to paraprotein deposition in the kidney.

Workup

of the brain was performed looking for a cerebral cause. The brain appeared normal. Close inspection revealed a lytic lesion in the left temporal bone (right side of image), and focused reconstructions of the petrous temporal bones confirmed a lytic lesion involving the mastoid segment of the facial nerve canal. Red arrows: lesion; green arrow: normal contralateral facial nerve canal. The lytic lesion was one of many in the skull and is consistent with a myeloma deposit.]]

The workup of suspected multiple myeloma includes a skeletal survey. This is a series of X-rays of the skull, axial skeleton and proximal long bones. Myeloma activity sometimes appear as "lytic lesions" (with local disappearance of normal bone due to resorption), and on the skull X-ray as "punched-out lesions" (pepper pot skull). Magnetic resonance imaging (MRI) is more sensitive than simple X-ray in the detection of lytic lesions, and may supersede skeletal survey, especially when vertebral disease is suspected. Occasionally a CT scan is performed to measure the size of soft tissue plasmacytomas. Bone scans are typically not of any additional value in the workup of myeloma patients (no new bone formation, lytic lesions not well visualized on bone scan).

A bone marrow biopsy is usually performed to estimate the percentage of bone marrow occupied by plasma cells. This percentage is used in the diagnostic criteria for myeloma. Immunohistochemistry (staining particular cell types using antibodies against surface proteins) can detect plasma cells which express immunoglobulin in the cytoplasm but usually not on the surface; myeloma cells are typically CD56, CD38, CD138 positive and CD19 and CD45 negative. In MM, lack of a proliferative clone makes conventional cytogenetics informative in only ~30% of cases.

1. Virtual karyotyping identified chromosomal abnormalities in 98% of MM cases
2. del(12p13.31) is an independent adverse marker
3. amp(5q31.1) is a favorable marker
4. The prognostic impact of amp(5q31.1) over-rides that of hyperdiploidy and also identifies patients who greatly benefit from high-dose therapy.

Array-based karyotyping cannot detect balanced translocations, such as t(4;14) seen in ~15% of MM. Therefore, FISH for this translocation should also be performed if using SNP arrays to detect genome-wide copy number alterations of prognostic significance in MM.

Diagnostic criteria

In 2003, the International Myeloma Working Group

• Stage I: β₂-microglobulin (β2M) < 3.5 mg/L, albumin >= 3.5 g/dL
• Stage II: β2M < 3.5 and albumin < 3.5; or β2M >= 3.5 and < 5.5
• Stage III: β2M >= 5.5

Durie-Salmon staging system

First published in 1975, the Durie-Salmon staging system is still in use:

• stage I: all of
  • Hb > 10g/dL
  • normal calcium
  • Skeletal survey: normal or single plasmacytoma or osteoporosis
  • Serum paraprotein level < 5 g/dL if IgG, < 3 g/dL if IgA
  • Urinary light chain excretion < 4 g/24h
  • stage II: fulfilling the criteria of neither I nor III
  • stage III: one or more of
    • Hb < 8.5g/dL
    • high calcium > 12 mg/dL
    • Skeletal survey: Three or more lytic bone lesions
    • Serum paraprotein > 7g/dL if IgG, > 5 g/dL if IgA
    • Urinary light chain excretion > 12g/24h

Stages I, II, and III of the Durie-Salmon staging system can be divided into A or B depending on serum creatinine:

• A: serum creatinine < 2 mg/dL (< 177 umol/L)
• B: serum creatinine > 2 mg/dL (> 177 umol/L)

Further Reading

• What is Multiple Myeloma?
• Multiple Myeloma Symptoms
• Multiple Myeloma Pathophysiology
• Multiple Myeloma Treatment
• Multiple Myeloma Epidemiology

This article is licensed under the Creative Commons Attribution-ShareAlike License. It uses material from the Wikipedia article on "Multiple myeloma" All material adapted used from Wikipedia is available under the terms of the Creative Commons Attribution-ShareAlike License. Wikipedia® itself is a registered trademark of the Wikimedia Foundation, Inc.