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 pati ents with multiple myeloma (MM) have reported conflicting data regarding th e exact levels of clonal B cells and the existence of clonal cells in the C D34 compartment. In this report we show that high numbers of clonal cells w ith a phenotype of late-stage B cells or pre-plasma cells were present in t he 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.