[1430] A Comparative Study of Multiple Myeloma with Two Independent Clones and Those with a Single Clone

Geling Li, Albert S Braverman, Constantine A Axiotis. SUNY Downstate Medical Center, Brooklyn, NY; Kings County Hospital Center, Brooklyn, NY

Background: About 1% of multiple myeloma (MM) patients have more than one M component detectable in the serum. This might be due to class switching within a plasma cell clone, or to two independent clones. In the latter case, the variable domains of Ig differ in their amino acid sequence and idiotype. No differences between the pathological and clinical phenomena associated with polyclonal and monoclonal gammopathies have been identified, due to the rarity of the former.
Design: We report 12 MM patients whose serum immunofixation studies clearly indicated two M components. To exclude cases of class switching within a single clone, we do not accept those patients whose two M components displayed same light chains, but different Ig isotypes; in some excluded cases, the second M component consisted only of light chains as those present in the Ig molecule. Controls were 38 MM patients with a single M component: 21 IgGk, 9 IgGλ, and 8 IgAk. Four of the 12 biclonal patients, but none of the monoclonal patients were HIV+. The % of BM plasma cells, Hb, platelet counts, albumin and creatinine levels at the time of biopsy, in the biclonal and monoclonal patients, were compared.
Results: 50% of the biclonal patients had <20% bone marrow (BM) plasma cells. In contrast, 4.8% of the IgGk, 12.5% of the IgGλ and 14.3% of the IgAk monoclonal patients had <20% plasma cells in the BM. BM plasmacytosis displayed a strong inverse correlation with anemia severity (correlation co-efficient -0.773). The bi-clonal group had a hemoglobins (Hb) of 10.14 ±1.46 g/dL, while the IgGk, IgGλ and IgAk groups had Hbs of 7.54±1.77 g/dL, 8.8 ±1.44 g/dL and 7.55±1.73 g/dL, respectively; these differences were significant (p=0.0001, 0.0498, and 0.002). Similar differences were observed in the 8 remaining biclonal patients, 25% of whom had <20% plasma cells, with a Hb of 10.23±1.73 g/dL. This, too, was significantly higher than the Hb's of the monoclonal IgGk and IgAk; p=0.001 and 0.008. The platelet counts, albumin and creatinine levels were similar in mono- and biclonal groups, regardless of HIV status.
Conclusions: The high incidence HIV infection in the biclonal patients may be related to pre-existing polyclonal B cell hyperactivation. The BM plasma cell concentrations and Hb levels suggest that biclonality occurs in those with less advanced disease than that of the monoclonal patients. The reason for this difference is unclear but may indicate a difference in pathogenesis. Other clinical manifestations, response to therapy and relapse-free survival in the two groups are being investigated.
Category: Hematopathology

Wednesday, March 6, 2013 1:00 PM

Poster Session VI # 224, Wednesday Afternoon

 

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