High numbers of clonal CD19+ cells in the peripheral blood of a patient with multiple myeloma

Recent studies concerning the numbers of circulating clonal B cells in patients with multiple myeloma (MM) have reported conflicting data regarding the exact levels of clonal B cells and the existence of clonal cells in the CD34 compartment. In this report we show that high numbers of clonal cells with a phenotype of late-stage B cells or pre-plasma cells were present in the peripheral blood (PB) of a patient with MM. During treatment the initial high level of PB clonal cells was markedly reduced and remained low (<1%) post transplant, even after disease progression. In addition, we found that the MM clone did not include a B-progenitor population defined by CD34.