Biclonal gammopathies: The simultaneous presence of more than one type of M-protein can be seen in as many as 5% of patients with monoclonal gammopathies. This likely represents the proliferation of two separates clones of plasma cells, producing M-proteins of different immunoglobulin classes. Patients with three different types of M-proteins also have been reported. Most of these were associated with malignant lymphoproliferative disorders, though a few were of undetermined significance. Kyle et al. reported on 57 patients with biclonal gammopathy, of whom 37 had a biclonal gammopathy of undetermined significance.92 These patients had clinical features indistinguishable from those with monoclonal gammopathies. The remaining patients with a biclonal gammopathy had myeloma, macroglobulinemia, or another lymphoproliferative disorder. Nilsson et al. found 20 patients (2%) from among 1034 patients with monoclonal gammopathy, who had two distinct monoclonal spikes; 3 were associated with lymphoma, 7 with myelomatosis, 9 with monoclonal gammopathy of undetermined significance (MGUS), and 1 with lupus erythematosus disseminatus.93
Idiopathic Bence Jones Proteinuria: Patients may present with isolated monoclonal FLCs in the urine, or Bence Jones proteinuria. Several patients have been reported with Bence Jones proteinuria, with disease that has remained stable over long periods of follow up. Kyle reported nine patients with Bence Jones pro-teinuria of over 1 g/24 hours with no serum M-protein and no evidence of another plasma cell proliferative disorder.94 95 While symptomatic myeloma developed in three of these patients at 8-21 years of follow up, two were followed for 12 years with no evidence of progression. Similar outcomes have been reported by others.96 While patients with idiopathic Bence Jones proteinuria can stay stable over long periods, some studies have suggested an increased risk of progression in patients with light chain proteinuria, and they need to be followed closely.
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