IMMUNOGLOBULIN GENE REARRANGEMENT IN PLASMA-CELL DYSCRASIAS - DETECTION OF SMALL CLONAL CELL-POPULATIONS IN PERIPHERAL-BLOOD AND BONE-MARROW

The bone marrow (BM) and peripheral blood (PB) samples of 71 patients with plasma cell dyscrasias were analysed by the Southern blot techniq ue for the presence of clonal immunoglobulin (Ig) gene rearrangements. 53% of BM samples examined were archival material such as air dried B M slides or frozen trephine biopsies. The results were related to bone marrow plasmacytosis as determined by cytology and flow cytometry, an d other clinical parameters. Clonal Ig gene rearrangements were found in BM samples of 45 (83%) of 54 MM patients and in 3 of 6 patients wit h monoclonal gammopathy of unknown significance (MGUS). Clonal cell po pulations in the PB were detected in 11 (30%) of 37 examined MM patien ts, but in none of the patients with MGUS or solitary plasmacytoma of bone. PB involvement was associated with progressive disease. Circulat ing monoclonal cells were significantly associated with higher M-prote in levels (p < 0.05). Thus, circulating clonal precursor cells are enc ountered more frequently in active MM.