a monoclonal protein include back pain, osteoporosis disproportionate to age, pathologic fracture, osteolytic or sclerotic bone lesions, recurrent sinopulmonary infections, progressive peripheral neuropathy, infiltrative or restrictive cardiomyopathy, and Raynaud’s phenomenon. It must, however, be noted that in these conditions a monoclonal protein may not always be detected by standard testing, and further evaluation may be needed to confirm or exclude an underlying plasma cell or lymphoproliferative disorder, particularly if the index of suspicion is high. Most patients with monoclonal protein are asymptomatic, especially those in whom a routine blood abnormality leads to further testing, resulting in the identification of a monoclonal protein. A simple algorithm taking into consideration the various tests available and clinical presentation is shown in Figure 95.2. Although there may be some overlap, following this algorithm should lead to the correct diagnosis in most cases.
TABLE 95.1 CLASSIFICATION OF MONOCLONAL PROTEINS
may fail to identify the presence of a monoclonal protein, especially in cases where there is only minimal production of the monoclonal protein, or minimal amounts of immunoglobulin free light chains.24 Currently in such cases performing immunofixation despite a negative protein electrophoresis or using the serum free light chain analysis may be the only way to confirm the presence of an underlying clonal disorder, although tandem mass spectroscopy methods are currently being explored.21, 25, 26 A monoclonal protein spike should not be confused with a polyclonal increase in immunoglobulin, which usually will be seen as a broad-based band in the gamma region and is not associated with a clonal cell disorder27 (Fig. 95.5).
FIGURE 95.4. Images of a serum protein electrophoresis and immunofixation depicting a monoclonal protein.
lymphoproliferative disorder, even if the protein electrophoresis is negative for an M-spike. Capillary zone electrophoresis with immunosubtraction is an automated system that is slightly more sensitive than high-resolution agarose gel electrophoresis and can be used in the identification, subtyping, and measurement of the M-protein.17, 19 This method is laborious and time consuming, however, making it less frequently used for typing of the monoclonal protein.