Background and purpose: To investigate the prevalence of monoclonal gammopathy, the frequency of associated diseases, and the laboratory features useful in the differential diagnosis and prediction of associated complications.
Materials and methods: From January 1994 through December 1998, 11,510 serum samples and 1,555 urine samples from 10,974 Taiwanese patients requiring electrophoresis study were examined for the presence of monoclonal protein by electrophoresis on cellulose acetate membrane and immunofixation electrophoresis (IFE).
Results: Two hundred and eighty seven cases (2.6%) of monoclonal gammopathy were found. Of these, 136 (47.4%) had multiple myeloma, 84 (29.3%) had monoclonal gammopathy of undetermined significance (MGUS), 53 (18.5%) had other lymphoproliferative disorders (LPD), eight (2.8%) had polyneuropathy, organomegaly, endocrinopathy, monoclonal gammopathy, skin pigmentation (POEMS) syndrome, and six (2.1%) had cryoglobulinemia. Immunoglobulin A (IgA) monoclonal protein was more often associated with myeloma than LPD (25 vs 3.8%, p = 0.002); monoclonal light chains were more often associated with myeloma than MGUS (17% vs 3.6%, p = 0.006). Biclonal gammopathy was more often associated with MGUS than myeloma (10.7 vs 1.5%, p = 0.014). Hypogammaglobulinemia was common in patients with myeloma (70%) but rare in patients with LPD (20%, p < 0.001) and in those with MGUS (5%, p < 0.001). Concomitant polyclonal hypergammaglobulinemia was rare in patients with myeloma (5%), but common in patients with LPD (53%, p < 0.001) or MGUS (27%, p < 0.001). Patients with lambda chain myeloma had the highest risk (100%) of developing renal insufficiency. Our myeloma patients were also at increased risk of developing myelomatous pleural effusions than previously reported.
Conclusions: The lower frequency of MGUS in this study than previously reported may have been due to differences in patient selection, laboratory methods, and the presence of local diseases. The presence of POEMS syndrome and cryoglobulinemia, the very high association of lambda chain myeloma with renal failure, and the higher occurrence of myelomatous effusion than previously reported probably reflected local disease patterns.