VII. TEACHING POINTS

1. A monoclonal (M-) protein increase consists of an excess of one type of heavy chain and one type of light chain. A polyclonal gammopathy usually consists of more than one type of heavy chain and both kappa and lambda light chains.
2. The differentiation of a monoclonal and polyclonal increase in immunoglobulins is essential. Patients with a monoclonal increase of immunoglobulins have either a neoplastic process or a potentially malignant disease, whereas patients with a polyclonal increase in immunoglobulins have a reactive or inflammatory process.
3. Typically, a monoclonal protein is characterized by a tall, narrow-based spike on the densitometer pattern or a localized band on the agarose gel. However, a small monoclonal protein in the serum may be obscured by normal components. Immunofixation is needed to determine whether a monoclonal protein is present and to determine its type.
4. A 24-hour urine specimen must be collected and measured for total protein, electrophoresis, and immunofixation. Again, small amounts of monoclonal light chain may not produce a spike. Consequently, immunofixation of an adequately concentrated urine specimen is needed.
5. Multiple myeloma is characterized by end-organ damage. (CRAB = hypercalcemia, renal insufficiency, anemia and lytic bone lesions.)
6. In treating multiple myeloma one must first decide whether the patient is a candidate for an autologous stem cell transplant.
7. The amount of monoclonal protein in the urine is a direct reflection of the number of monoclonal plasma cells in the bone marrow and is thus a measure of tumor mass.
8. The presence of a monoclonal light chain in the urine of a patient with nephrotic syndrome is almost always associated with primary amyloidosis (AL) or light chain deposition disease.
9. The presence of a monoclonal protein in the serum or in the urine in a patient with an unexplained nephrotic syndrome, congestive heart failure, sensorimotor peripheral neuropathy, carpal tunnel syndrome, or orthostatic hypotension is strongly suggestive of primary amyloidosis (AL).
10. Tissue must be obtained to make a diagnosis of primary amyloidosis. (See illustration below.)

    

    Adapted from:
    Primary systemic amyloidosis: clinical and laboratory features in 474 cases. Sem Hematol 1995;32:45-59.

    A subcutaneous fat aspirate and/or a positive bone marrow stain for amyloid is found in 90% of patients. If the clinician still suspects primary amyloidosis in a patient with a negative subcutaneous fat aspirate and bone marrow biopsy, he/she should obtain tissue from a clinically involved organ.

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