Monoclonal B cell lymphocytosis is a precursor to chronic lymphocytic leukemia. An article published in the February 27 issue of Blood demonstrated that healthy blood donors in a Midwestern city in the United States had a surprisingly high incidence of monoclonal B cell lymphocytosis. MBL was detected in 7.1% of 2098 unique donors. The majority of cases had low count MBL which has a low risk of evolving into CLL, but 3.4% had clinical MBL with greater than 500 monoclonal B lymphocytes per uL. This latter category has a significant risk of progressing to CLL.
This study raises the possibility that premalignant lymphocytes could be transmitted to recipients of blood transfusions. If so, then donors may need to be screened for MBL in the future. A lookback study of donors with MBL may help to answer this important question. Also, no one knows if the risk is mitigated by current leukocyte reduction methods or irradiation.
Shim, YK, etal. Monoclonal B-cell lymphocytosis in health blood donors: an unexpectedly common finding. Blood. 2014;123(9):1319-1326.
Stetler-Stevenson, M. Monoclonal B-cell lymphocytosis in donors. Blood. 2014;123(9):1281-1282.